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Abstract: The Princeton chert is one of the most completely studied permineralized floras of the Paleogene. Remains of over 30 plant taxa have been described in detail, along with a [...]

A flora from Thomas Ranch near Princeton, British Columbia, Canada, is assessed for biodiversity and paleoclimate. This latest Early to early Middle Eocene flora occurs in the Allenby Formation. Seventy-six megafossil morphotypes have been recognized, representing at least 62 species, with 29 identified to genus or species. Common taxa include Ginkgo L., Metasequoia Miki, Sequoia Endl., Abies Mill., Pinus L., Pseudolarix Gordon, Acer L., Alnus Mill., Betula L., Fagus L., Sassafras J Presl, Macginitiea Wolfe & Wehr, Prunus L., and Ulmus L. More than 70 pollen and spore types are recognized, 32 of which are assignable to family or genus. The microflora is dominated by conifers (85%-97% abundance), with Betulaceae accounting for most of the angiosperms. The Climate Leaf Analysis Multivariate Program (CLAMP) calculates a mean annual temperature (MAT) of 9.0 ± 1.7°C and bioclimatic analysis (BA) calculates a MAT of 12.8 ± 2.5°C. Coldest month mean temperature (CMMT) was >0°C. Mean annual precipitation (MAP) was >70 cm/year but is estimated with high uncertainty. Both the CLAMP and BA estimates are at the low end of the MAT range previously published for other Okanagan Highland localities, indicating a temperate climate consistent with a mixed conifer-deciduous forest. Key words: Eocene, leaf morphotype, Okanagan Highlands, paleoclimate reconstruction, paleoenvironment, palynology. Resume: Les auteurs evaluent la biodiversite d'une flore provenant de Thomas Ranch pres de Princetown en Colombie canadienne, en relation avec le paleoclimat. Cette derniere flore allant du debut de l'Eocene jusqu'au debut de l'Eocene moyen, se retrouve dans la formation de Allenby. Ils ont reconnu 76 morphotypes de mega fossiles, representant au moins 62 especes, dont 29 entites identifiees au genre ou a l'espece. Parmi les taxa communs, on retrouve les Ginkgo L., Metasequoia Miki, Sequoia Endl., Abies Mill., Pinus L., Pseudolarix Gordon, Acer L., Alnus Mill., Betula L., Fagus L., Sassafras J Presl., Macginitiea Wolfe & Wehr, Prunus L., et Ulmus L. Ils ont egalement reconnu plus de 70 types de pollens et de spores, dont 32 peuvent etre classifies a l'echelle de la famille ou du genre. La microflore est dominee par des coniferes (abondance de 85-97 %), avec des Betulaceae constituant la plupart des angiospermes. A l'aide du programme d'analyse multivariee pour le climat et les feuilles (PAMCF), on a calcule une temperature annuelle moyenne (TAM) de 9.0 ± 1.7°C et avec l'analyse bioclimatique (AB), une TAM 12.8 ± 2.5°C avec une temperature moyenne du mois le plus froid (TMMF) >0°C. Estimee avec une forte incertitude, la precipitation mensuelle moyenne (PMM) etait >70 cm/an. Les estimations des PAMCF et AM se retrouvent dans le bas de l'eventail de la TAM deja publiee pour d'autres localites des Okanagan Highland, ce qui indique un climat thermique congruent avec une foret mixte coniferes-decidus. [Traduit par la Redaction] Mots-cles: Eocene, morphotypes foliaires, Okanaga Highland, paleoclimat reconstruction, paleo environnement, palynologie., Introduction Fossil plants from the Princeton area, British Columbia, Canada, were first noted by Sir J. William Dawson in 1890, followed by a detailed description of fossils collected from the [...]

In volume 97(2) of the American Journal of Botany (pp. 268-275), we published an article entitled 'Structural, physiological, and stable carbon isotopic evidence that the enigmatic Paleozoic fossil Prototaxites formed from rolled liverwort mats'. Here, we respond to a letter and a commentary on our article in the present issue, welcoming this opportunity to continue the scientific dialogue about an issue that has long been stimulating and controversial. For the reader's benefit, we first briefly describe the recent scholarly context of our article. doi: 10.3732/ajb.1000172

New structural, nutritional, and stable carbon isotope data may resolve a long-standing mystery--the biological affinities of the fossil Prototaxites, the largest organism on land during the Late Silurian to Late Devonian (420-370 Ma). The tree trunk-shaped specimens, of varying dimensions but consistent tubular anatomy, first formed prior to vascular plant dominance. Hence, Prototaxites has been proposed to represent giant algae, fungi, or lichens, despite incompatible biochemical and anatomical observations. Our comparative analyses instead indicate that Prototaxites formed from partially degraded, wind-, gravity-, or water- rolled mats of mixotrophic liverworts having fungal and cyanobacterial associates, much like the modern liverwort genus Marchantia. We propose that the fossil body is largely derived from abundant, highly degradation-resistant, tubular rhizoids of marchantioid liverworts, intermixed with tubular microbial elements. Our concept explains previously puzzling fossil features and is consistent with evidence for liverworts and microbial associates in Ordovician-Devonian deposits, extensive ancient and modern marchantioid mats, and modern associations of liverworts with cyanobacteria and diverse types of fungi. Our interpretation indicates that liverworts were important components of Devonian ecosystems, that some macrofossils and microfossils previously attributed to 'nematophytes' actually represent remains of ancient liverworts, and that mixotrophy and microbial associations were features of early land plants. Key words: C isotope; liverwort; mixotrophy; Marchantia; marchantioid; Prototaxites; rhizoid. doi: 10.3732/ajb.0900322

A distinctive, extinct type of flower and fruit is described based on coalified compression and impression fossils from the Eocene lake bed deposits of McAbee, British Columbia. Dillhoffia cachensis gen. et sp. nov. has an elongate-ellipsoidal fruit with an epigynous, completely connate funnelform calyx 1.8-2.9 cm in diameter, with an unlobed, orbicular margin. The fruit narrows apically into a single style divided into four slightly recurved stigmatic aims. Fruits are pedicellate, borne in globose heads. Stamens, pollen, and internal fruit morphology remain unknown, but the available details of gynoecial and perianth morphology present a suite of characters not encountered in any known extant genus, and the familial affinities remain uncertain. This is noteworthy, because many other elements of the same Eocene flora represent extant genera with clear familial assignments such as Cunninghamia, Ginkgo, Aesculus, Alnus, Betula, Dipteronia, Fagus, Trochodendron, and Ulmus. Key words: Eocene, paleobotany, flower, fruit, McAbee, British Columbia. Les auteurs decrivent un type de fleurs et de fruits eteints bien caracterises a partir de fossiles carbonises par impression ou compression, provenant des depots de fond du lac Eocene, a McAbee, en Colombie canadienne. Le Dillhoffia cachensis gen. et sp. nov. montre un fruit allonge ellipsoide avec un calice epigyne completement conne infundibiliforme, mesurant 1.8-2.9 cm de diametre, avec une marge orbiculaire non lobee. Les fruits s'amenuisent apicalement en simple style divise en quatre bras stigmatiques legerement recourbes. Les fruits sont portes sur des pedicelles a partir de cimes globulaires. Les etamines, le pollen, et la morphologie interne demeurent inconnus, mais les details disponibles sur la morphologie du perianthe et du gynecee presentent une suite de caracteres qu'on ne retrouve dans aucun genre existant connu, et les affinites familiales demeurent incertaines. Ceci est remarquable puisse que plusieurs autres elements de la meme flore Eocene representent des genres existant actuellement avec des attributions familiales nettes, tels que les Cunninghamia, Ginkgo, Aesculus, Alnus, Betula, Dipteronia, Fagus, Trochodendron et Ulmus. Mots-cles : Eocene, paleobotanique, fleur, fruit, McAbee, Colombie canadienne. [Traduit par la Redaction], Introduction The Eocene lake sediments of McAbee, near Cache Creek, British Columbia, yield a diverse flora including at least 14 conifers and 67 angiosperms (Dillhoff et al. 2005). Dominant dicots [...]

The Icacinaceae occur pantropically today, but are well represented by fossil fruits of the warm Early Middle Eocene, when tropical plants that currently occupy low latitudes were more widely distributed in higher latitudes. Members of this family are first known in the Late Cretaceous; however, fossil fruits of tribe Iodeae are quite rare before the Eocene. In this paper we describe the first formally recognized Late Paleocene icacinaceous taxa from western North America. We name two new species of Icacinicarya based on anatomically preserved fruits and establish a new genus, Icacinicaryites, for impressions with a strong similarity to Icacinicarya that lack anatomical preservation. These new records from the Almont/Beicegel Creek flora in North Dakota and several localities in Wyoming, Colorado, and Montana complement records known from the Early Eocene of England and document an increased diversity of Iodeae and related forms in the Paleogene of western North America. Key words: Euasterid; fossil endocarp; Icacinaceae; Icacinicarya; Iodeae; North Dakota; Paleocene.

Altingia (Altingiaceae) is a tropical to subtropical Asian genus of lowland trees for which 5-15 species have been recognized. Morphological diversity, particularly of the mature infructescence, has been poorly known, especially for species with relatively localized and narrow distributions, and our understanding of Altingia has lagged behind that of its close temperate relative Liquidamhar (sweet gum). In this contribution, mature infructescence structure, at the levels of anatomy, morphology, and micromorphology, and some distinctive inflorescence features, are described for five recognized species of Altingia, some for the first time. In the phylogenetic framework of both morphology and molecules, characters of Altingia contrast with those of Liquidambar and suggest that character evolution within Altingiaceae is at least partly related to geographic and climatic distribution. Differences in rates of evolution and morphological convergence suggest complex patterns of diversification in Altingiaceae at several different phylogenetic levels: (1) at the deep nodes, characters of the stem lineage fossil Microaltingia persist into crown group Altingiaceae, morphological stasis; (2) at the generic level, convergence within both Liquidambar and Altingia toward their respective habitats; (3) at the infrageneric level, morphological divergence in species diversification within Altingia, in response to diverse habitats of the eastern Asian subtropics; and (4) within the intercontinental disjunct species pair L. orientalis-L, styraciflua, morphological stasis. Key words: Altingia; Altingiaceae; biogeography; infructescence; morphological stasis.

High resolution x-ray computed tomography (HRXCT) was used to image pyritized fossil fruits from the Lower Eocene London Clay flora to test the utility of this technique for paleobotanical application. The combination of carbon-pyrite preservation and void spaces between fruit and seed layers within fossils provides differences in density and composition that enable excellent imaging. Fossil fruits of Palaeorhodomyrtus subangulata (Bowerbank) Reid & Chandler (Myrtaceae) were investigated in situ within their silicone fluid conservation medium, which protects these unstable fossils from oxygen and humidity. HRXCT recovers taxonomically informative anatomical and morphological detail and provides a means of nondestructive examination of delicate type materials and other important specimens. These results suggest that HRXCT will be applicable to a broad spectrum of pyritized fossils to record structural details in inherently unstable materials. Key words: fossil fruits and seeds; high resolution x-ray computed tomography (HRXCT); London Clay; paleobotanical techniques; pyrite permineralization.

Paleoactea nagelii Pigg & DeVote gen. et sp. nov. is described for a small, ovoid ranunculaceous fossil fruit from the Late Paleocene Almont and Beicegel Creek floras of North Dakota, USA. Fruits are 5-7 mm wide, 4.5-6 mm high. 10-13 mm long, and bilaterally symmetrical, containing 10-17 seeds attached on the tipper margin in 2-3 rows. A distinctive honeycomb pattern is formed where adjacent seeds with prominent palisade outer cell layers abut. Seeds are flattened, ovoid, and triangular. To the inside of the palisade cells, the seed coat has a region of isodiametric cells that become more tangentially elongate toward the center. The embryo cavity is replaced by an opaline cast. This fruit bears a striking resemblance to extant Actaea, the baneberry (Ranunculaceae), an herbaceous spring wildflower of North Temperate regions. A second species, Paleoactaea bowerhanki (Reid & Chandler) Pigg & DeVore nov. comb., is recognized from the Early Eocene London Clay flora, based on a single fruit. This fruit shares most of the organization and structure of P. nagelii but is larger and has a thicker pericarp. This study documents a rare Paleocene occurrence of a member of the buttercup family, a family that is today primarily herbaceous, and demonstrates a North Atlantic connection for an Actaea-like genus in the Paleogene. Key words: Actaea; Almont; London Clay; Paleocene; Ranunculaceae.

The sweet gum genus Liquidambar (Altingiaceae) has two species in eastern Asia, one in eastern North America, and one in western Asia. Mature infructescences are studied to provide anatomical, morphological, and micromorphological details, some of which are newly recognized. Homology is suggested between extrafloral spinose processes of L. formosana and L. acalycina, braid-like ornamentation of L. styraciflua, and broad intercarpellate areas of L. orientalis. Morphology, position, number, and the presence of similar structures in the closely related Hamamelidaceae s.s. support their derivation from sterile flowers. Morphological cladistic analysis using 43 characters supports the monophyly of Liquidambar with Altingia as its sister. The matK analysis contrastingly places Altingia sister to the L. acalycina-L, formosana clade, rendering Liquidambar paraphyletic. Discordance between morphological and matK data sets may result from both different rates of morphological evolution and convergence. Several similarities between Altingia and L. acalycina are symplesiomorphic in the morphological cladistic analysis. Microaltingia apocarpela, from the Cretaceous of eastern North America, documents the earliest known fossil divergence within Altingiaceae. The Miocene Liquidambar changii of western North America is sister to a clade of extant Liquidambar species. Consideration of this fossil evidence reveals complex intercontinental biogeographic disjunctions in Altingiaceae. Key words: Altingiaceae; biogeography, infructescence; Liquidambar, phylogeny.

Shirleya grahamae Pigg & DeVore gen. et sp. nov. (Lythraceae) is established for silicified fruits from the middle Miocene Yakima Canyon of central Washington State, USA. The capsules are 10 mm long x 11.5-12.5 mm wide, enclosed in a persistent floral tube and contain 5-7 locules. They are loculicidally dehiscent, fracturing into fragments and leaving the central axis free. Placentation is axile. Five to seven mature seeds are tightly packed per locule, often with several smaller seeds. Seeds are winged, anatropous, and narrowly attached subapically to the central axis, curving basally and radially within the fruit. They are up to ~4.6 mm long x 1.9 nun wide, with a small, triangular embryo cavity and a prominent distal wing. The inflated wing is filled with a bilobed parenchymatous pad of tissue with a central cavity. Shirleya grahamae is assigned to the Lythraceae, and is most similar to Lagerstroemia, based on the synapomorphies of distally winged seeds and revolute cotyledons. Shirleya differs from Lagerstroemia in seed arrangement, and pericarp and wing anatomy. This study provides the first anatomical information about a Miocene Lagerstroemia-like fruit and documents further diversity of the Lythraceae in the Neogene of northwestern North America. Key words: fossil fruit; Lagerstroemia; Lythraceae; Miocene; permineralization.

Liquidambar changii Pigg, Ickert-Bond & Wen sp. nov. (Altingiaceae) is established for anatomically preserved, middle Miocene infructescences from Yakima Canyon, Washington, USA. Specimens are spherical, ~2.5 cm in diameter, and have ~25-30 tightly packed, bilocular fruits per head. Fruits are 3.4-4.7 mm wide x 2.6-3.5 mm long and wedge shaped, fused at the base, and free distally. Each locule contains 1-2 mature, elongate seeds proximally and 5 9 aborted seeds of more irregular shape distally. Mature seeds are 1.5 mm long x 1.2 mm wide, elongate, and triangular transversely, with a slight flange. Seeds have a seed coat for which three zones can be well defined, a uniscriate outer palisade layer, a middle region of isodiametric cells comprising most of the integument, and a uniseriate inner layer of tangentially elongate cells lining the embryo cavity. Liquidambar changii is most similar to the eastern Asian L. acalycina H.-T. Chang on features of infructescence, fruit, and seed morphology and quite unlike the North American L. styraciftua L. and other species. Such a close relationship between these two species supports a Beringian biogeographic track between eastern Asia and western North America during the Miocene. Previous phylogenetic and allozyme analysis of modern Liquidambar demonstrates a close relationship between North American-western Asian taxa and suggests a North Atlantic biogeographic track in the middle Miocene. Together, these biogeographic tracks underscore the complexity of the biogeographic history of the Altingiaceae in the Northern Hemisphere throughout the Neogene. Key words: Altingia; Altingiaceae; biogeography; fossil fruit; infructescenee; Liquidambar; Miocene; silicification.

Clevelandodendron ohioensis Chitaley & Pigg gen. et sp. nov. is an almost entire lycopsid plant known from a single compressed specimen from the Cleveland Shale member of the Upper Devonian Ohio Shale. This unique specimen is 125 cm long, consisting of an unbranched, slender, monopodial axis with a partially preserved plant base bearing thick appendages at one end, and a compact, terminal ovoid bisporangiate strobilus at the other. The stem is 2 cm wide for most of its length. Visible on the decorticated stem surface are helically arranged, elongate leaf traces and laterally compressed, slender leaves along the stem margin. The plant base bears 4-6 thick appendages. The terminal strobilus is compact, ovoid, 9 cm long and up to 6 cm wide, morphologically similar to those of some Lepidodendrales, and bears helically arranged sporophyll/sporangium complexes with narrow bases and distal laminae up to 18 mm long, turned upward. Megaspores are 320-360 [[micro]meter], trilete and laevigate, lacking a gula; microspores are 30-42 [[micro]meter], trilete, indistinctly punctate and possibly assignable to Calamospora or Punctatisporites. Clevelandodendron demonstrates that slender unbranched lycopsids with an isoetalean plant habit similar to the Carboniferous genera Chaloneria and Sporangiostrobus and Triassic Pleuromeia-like forms were present as early as the Late Devonian. The early occurrence of this unique habit suggests that diversification within the isoetalean clade sensu Rothwell and Erwin (including both Isoetales and Lepidodendrales) was well established prior to the Carboniferous. Key words: isoetalean; Late Devonian; lycopsid; Pleuromeia.

Stems and buds of Glossopteris skaarensis Pigg and buds of G. schopfii Pigg from the Permian Skaar Ridge locality in the central Transantarctic Mountains, Antarctica demonstrate the first anatomically preserved glossopterids known with stem/leaf attachment. Stems of G. skaarensis are 1-12 mm in diameter (arithmetic mean of sample = 3.1 mm) with a broad pith, poorly defined primary xylem, and a zone of secondary xylem up to 6 mm thick. Pycnoxylic wood conforming to Araucarioxylon Kraus is composed of tracheids with uni- to biseriate oval to hexagonal bordered pits on radial walls, uniseriate rays one to a few cells high, and cupressoid to taxodioid cross-field pitting. Stems have a narrow zone of secondary phloem, aerenchymatous cortex with scattered sclereids, and sometimes a narrow periderm. Two wedge-shaped leaf traces each bifurcate to form four strands in the base of each petiole. Small axillary branches are vascularized by double branch traces that fuse at the margin of the main axis. Buds of G. skaarensis have leaves with narrow lateral laminae and a thickened midrib containing a wide lacuna, delicate vascular strands, and a prominent hypodermis. In contrast, buds of G. schopfii have uniformly thick leaves with prominent, circular vascular bundle sheaths. These anatomical details are used to reconstruct individual types of glossopterid plants, providing new information toward understanding the ecology and evolution of this important group of Permian seed plants.

A new species of the quillwort Isoetites, I. rolandii sp. nov. Ash and Pigg, is described from the Middle Jurassic Coon Hollow Formation in the Wallowa terrane in Hells Canyon, Oregon and Idaho. The new species is based on coalified impressions and mold-casts of an isoetaceous corm with narrow, elongate leaves, and isolated masses of leaves that have been studied using light microscopy. Plants are about 10 cm in maximum height and consist of cormose plant bases from 1.5 to 2.5 cm wide and 0.6 cm high bearing incomplete microphyllous leaves up to 8.4 cm long and 3.0 mm wide that taper to about 2.0 mm wide distally. Associated casts of sporophyll bases and sporangia contain spherical structures about 440 [mu]m in diameter that may represent megaspores. Based on the occurrence of complete plants, some specimen of I. rolandii are thought to have been preserved in situ. The new I Isoetites provides the first floristic evidence for the occurrence of an aquatic or semiaquatic paleoenvironment in the Wallowa terrane. It is also the first documented occurrence of Isoetes-like plants in the Jurassic of western North America.

Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern are described from the middle Miocene Yakima Canyon flora of central Washington State, USA. Identification of the W. virginica fossils is based on a combination of vegetative pinnules, rhizome and stipe anatomy, and fertile pinnules with indusiate sori and sporangia like those of extant W. virginica. Fronds are isomorphic. Vegetative pinnae are elongated and pinnatifid, with a secondary vein paralleling the midvein. Secondary veins of the pinnule lobe anastomose to form primary areoles and are either simple or dichotomize toward the margin. Rhizomes have a simple dictyostele with 3-5 cauline vascular bundles and often a sclerotic hypodermis. Leaf traces contain two large adaxial vascular bundles that occur laterally and adaxially, flanking an arc of 4-6 smaller bundles. Fertile pinnules have linear sori that are somewhat embedded in the laminae and are enclosed by a thin indusium. Leptosporangia display a vertical annulus and an elongated stalk. A second fern, Wessiea yakimaensis gen. et sp. nov., is represented by anatomically preserved branching rhizomes and attached frond bases that conform to the Onoclea-type pattern of rhizome and frond-base vasculature. Rhizomes have a simple dictyostele of 4-5 cauline meristeles. Leaf divergence is helical, with paired hippocampiform rachial traces. These two ferns occur in the same matrix with specimens of Osmunda wehrii. They demonstrate that filicalean fern assemblages similar to those of extant temperate floras were well established in western North America by the middle Miocene and further emphasize the exceptional species longevity of some homosporous pteridophytes. Key words: Blechnaceae; fossil Filicales; Miocene; silicified; Wessiea; Woodwardia virginica.

The middle Miocene Yakima Canyon flora (15.6 Ma) of central Washington state is one of the few Neogene fossil localities with anatomically preserved seed, fruit and vegetative remains. The detailed morphological and anatomical features preserved in these fossils have allowed us to recognize plants at several infrageneric levels, including section, subsection and extant species. Phytogeographic relationships and ecological associations can also be resolved to varying degrees. The presence of Woodwardia virginica (Blechnaceae), essentially identical to the modern Virginia chain fern of eastern North America, illustrates species longevity, well-known among homosporous ferns. Its occurrence with Osmunda wehrii (subgenus Osmunda) and a small onocleoid fern demonstrates that fern community associations in the Miocene were quite similar to those today. Quercus hiholensis is assignable to subgenus Quercus, section Quercus, and represents a white oak with developmental features that suggest annual fruit maturation, a highly derived feature within the genus, was established by the Miocene. Petrified Liquidambar infructescences showing features of section Liquidambar, provide the first evidence of fruit anatomy for this genus that today has a highly disjunct Asian-North American distribution. Conifers present include abundant taxodiaceous remains and Pinus foisyi (subgenus Pinus, section Pinus, subsection Oocarpae), which is most similar to modern California closed cone pines based on leaf and ovulate cone anatomy. In addition to other typical Miocene floristic elements such as Vitaceae, Cornaceae, and Rosaceae, the Yakima flora contains several fruits and seeds (cf. Rhamnaceae, Zygophyllaceae and Lythraceae) that probably represent extinct genera. The Yakima Canyon flora thus documents anatomy for plants of the widespread temperate flora of the middle Miocene during its maximum geographical distribution.

Trochodendron (Trochodendraceae) is documented from the early middle Eocene (49-50 Ma) Republic flora of Washington state, USA, based on distinctive leaves, an inflorescence and an isolated fruit. Leaves are morphologically similar to Miocene and extant Trochodendron, but demonstrate basally actinodromous venation like that of the extant sister genus Tetracentron rather than pinnate venation characteristic of the single extant species of Trochodendron. This new Trochodendron thus has venation that appears evolutionarily intermediate between these two genera as previously known and retains the palmate condition thought to be primitive within the Hamamelideae as a whole. Leaves are simple, symmetric, 3-8 cm long x 1.5-5 cm wide with an acute apex and acute to cuneate base, with exstipulate, striate, deeply caniculate petioles. Venation includes 2-3 pairs of lateral primaries, a marginal vein and up to three secondaries that diverge at angles of 40-45 degrees. Weak intersecondary veins anastomose at right angles into widely and irregularly spaced orthogonal reticulate tertiary veins. Leaves typically have an unlobed crenate margin with numerous small appressed chloranthoid (papillate) teeth in the apical portion of the lamina, while more basal portions are entire. Reproductive structures are quite similar to those of Miocene and extant forms. An infructescence specimen consists of a single woody axis 3.2 cm long and 16-23 mm wide that bears fruits on striated pedicels. Fruits have an acute base and truncate apex and sometimes show evidence of persistent recurved styles. Occurring in the same beds, is the extinct infructescence Nordenskioldia (Trochodendraceae) and its associated leaf Zizyphoides that show similiarities to those of Paleocene and Neogene relatives in North America, Europe and Asia. The presence at Republic of both a distinctive Trochodendron plant and Nordenskioldia and Zizyphoides remains demonstrates that the Trochodendraceae, today known exclusively from Asian endemics, was undergoing rapid diversification in the Eocene of western North America.

The first reported petrified acorns to show internal anatomical structure are here described from Middle Miocene ([approximately]15.6 million years old) chert of the Columbia River Basalt Group in Yakima Canyon, Washington. Quercus hiholensis Borgardt et Pigg sp. nov. is described from anatomical and morphological fruit features, as well as a little recognized anatomical feature, the umbilical complex. Acorns, each comprising a nut and its cupule, are up to 15.3 mm long and 18.8 mm wide with helically arranged, imbricate, tuberculate cupule scales. They show basal aborted ovules, short styles, broad stigmas, and lack grooves in their cotyledons. These characters and the developmental pattern seen in these fossil acorns demonstrate that Q. hiholensis conforms to genus Quercus (Fagaceae), subgenus Quercus, section Quercus (the white oaks). The correspondence of Q. hiholensis to the modern section Quercus reveals that the derived floral and fruit characters that distinguish section Quercus within the genus had evolved by the Middle Miocene. Key words: acorn; cupule; Fagaceae; fossil; fruit; Middle Miocene; paleobotany; Quercus.

Over 80 specimens of a permineralized fruit referable to the Comaceae (Mastixioideae) have been recovered from the Princeton chert (Allenby Formation) of British Columbia, Canada. Specimens were studied using a modified cellulose acetate peel technique for hydrofluoric acid. Fruits with endocarps 11 mm long and up to 10 mm in diameter have a smooth stone surface, one U-shaped locule in cross section and a germination valve that extends the length of the fruit. An epicarp (exocarp + mesocarp) composed of thin-walled parenchymatous cells, 1.2-1.5 mm thick, was found on one specimen. Remains of an apical disc with remnants of perianth parts are seen in three specimens. The endocarp is composed of interlocking fibers with scattered resin ducts and vascular tissue that parallels the edges of the valve. Seed integuments consist of a single external layer of large cells with brown staining contents and an inner zone of 2-4 thin-walled cells of smaller diameter lacking contents. Numerous septate fungal hyphae are usually present in the integumentary layers. These fruits most closely correspond to the fossil genus Mastixicarpum Chandler and extant Diplopanax Handel-Manzetti and add to our knowledge of the diversity and distribution of North American mastixioids during the Tertiary.

Many of the problems involving taxonomic delimitation of extant Isoetes are inherent in the fossil record as well. As with living Isoetes, the reduced plant body of Isoetes-like fossils provides a limited number of morphological features that have been shown in extant forms to be highly variable and often convergent. The problem is compounded by a lack of concordance in the definition of both the family Isoetaceae and the genus Isoetes in light of the rich and long-ranging fossil record of the isoetalean clade. The tendency of fossil plants to be found as disarticulated fragmentary remains adds further to the problem. Although members of the isoetalean clade can be recognized by the Late Devonian, the oldest fossil plants that can be confidently interpreted as having a reduced plant body like that of extant Isoetes are Jurassic, with a variety of additional forms occurring in the Cretaceous and Tertiary. The most obvious feature distinguishing modern Isoetes and Isoetes-like fossils from all other members of the isoetalean clade is a reduced, non-elongating stem axis. Aside from this and possibly a few other features, most of the unusual morphological features of Isoetes are shared by the entire clade.

Thirty-one specimens of petrified Liquidambar-like infructescences (Hamamelidaceae) have been studied from the middle Miocene Yakima Canyon flora of central Washington State, USA. The infructesences are globose fruiting heads consisting of dense clusters with numerous fruits per head. Each fruit is a 2-carpelled capsule with each carpel containing 1-2 mature seeds and up to 10 variously shaped abortive ovules. Mature seeds are 1.5 mm high x 1.2 mm wide, winged, and triangular in cross section. Seed integuments have a prominent outer layer of palisade cells, a middle region of isodiametric cells, and an inner lining of tangentially elongate cells. These fossils are the first anatomically preserved reproductive remains of Liquidambar-like plants to be described from northwestern North America and demonstrate similarities both to Tertiary forms such as the European Eocene Steinhauera Presl and Neogene Liquidamber as well as extant forms of subfamily Liquidambaroideae (Hamamelidaceae).

Highly opalized petrified plant, fungal, and possible animal remains are described from a middle Miocene (15.1-15.8 million year old) deposit in the Virgin Valley of northwestern Nevada, known as the 'Cessily-Anne' locality. Plant remains from this site, thought to represent a lake margin environment, include conifer and dicot wood, vegetative buds, seeds assignable to cf. Decodon (Lythraceae) and abundant pollen and spores. Fungi are represented by well preserved ascomycete perithecia with bicellular ascospores, multicellular conidia and several types of spores, sporangia and hyphae. Unusual cuticular sheaths that bear pointed spines and cellular sheaths with geometrically patterned ornamentation may represent animal remains. The exquisite preservation of this assemblage is thought to be the possible result of rapid deposition of volcanic ash or ash fall and plant debris into a lake. This volcanic slurry was then gelled into a silicified deposit.