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The term 'sphaerocrystals' (also sphaerites) in classic plant morphology was usually applied to spherical bodies visible in polarized light with a characteristic 'Maltese cross' and consisting of both inorganic and organic compounds. Initially sphaerocrystals were found in algal cells but were later also discovered in various organs of vascular plants (including seeds). Several authors noticed spherical particles on the seed surface and in testa cells of some Euphorbia species but a comprehensive study of this character in the genus (including the morphological origin of such particles) has not been carried out. We studied 72 species belonging to all 21 sections of Euphorbia subgenus Esula for presence of spherical particles on seed surface and in the testa using scanning, transmission, confocal laser electron microscopy, and light microscopy; histochemical and element analyses were also involved. We found that these particles have the same morphological features (including the demonstration of 'Maltese cross' in polarized light) as the 'classic' sphaerocrystals. We have recorded sphaerocrystals in 53 sampled species belonging to 20 sections of Euphorbia subgenus Esula ; they are localized mostly in mesotesta cells and in some species are exuded onto the seed surface where they are often aggregated into clusters. Sphaerocrystals were absent in the sampled species (with one exception) of one of the major clades of the subgenus, formed by E. sect. Helioscopia and E. sect. Holophyllum. The absence of sphaerocrystals in this early divergent lineage of E. subgen. Esula may be related with adaptation of species of this lineage to more mesic habitats. [ABSTRACT FROM AUTHOR]

Monographs are fundamental for progress in systematic botany. They are the vehicles for circumscribing and naming taxa, determining distributions and ecology, assessing relationships for formal classification, and interpreting long-term and short-term dimensions of the evolutionary process. Despite their importance, fewer monographs are now being prepared by the newer generation of systematic botanists, who are understandably involved principally with DNA data and analysis, especially for answering phylogenetic, biogeographic, and population genetic questions. As monographs provide hypotheses regarding species boundaries and plant relationships, new insights in many plant groups are urgently needed. Increasing pressures on biodiversity, especially in tropical and developing regions of the world, emphasize this point. The results from a workshop (with 21 participants) reaffirm the central role that monographs play in systematic botany. But, rather than advocating abbreviated models for monographic products, we recommend a full presentation of relevant information. Electronic publication offers numerous means of illustration of taxa, habitats, characters, and statistical and phylogenetic analyses, which previously would have been prohibitively costly. Open Access and semantically enhanced linked electronic publications provide instant access to content from anywhere in the world, and at the same time link this content to all underlying data and digital resources used in the work. Resources in support of monography, especially databases and widely and easily accessible digital literature and specimens, are now more powerful than ever before, but interfacing and interoperability of databases are much needed. Priorities for new resources to be developed include an index of type collections and an online global chromosome database. Funding for sabbaticals for monographers to work uninterrupted on major projects is strongly encouraged. We recommend that doctoral students be assigned smaller genera, or natural portions of larger ones (subgenera, sections, etc.), to gain the necessary expertise for producing a monograph, including training in a broad array of data collection (e.g., morphology, anatomy, palynology, cytogenetics, DNA techniques, ecology, biogeography), data analysis (e.g., statistics, phylogenetics, models), and nomenclature. Training programs, supported by institutes, associations, and agencies, provide means for passing on procedures and perspectives of challenging botanical monography to the next generation of young systematists. [ABSTRACT FROM AUTHOR]