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The localization of Ca2+ in cells of the periblem and dermatogen in the root meristem and the columella and peripheral cells of the root cap of maize was examined by the precipitation method of potassium pyroantimonate and EGTA-treatment. In periblem and dermatogen cells, Ca2+ was found to be localized in the nucleoplasm and granular zone of the nucleolus. Ca2+ was also found in most cell organelles: in the matrix in mitochondria, on the thylakoid membrane in proplastids, in the vacuoles and on the plasma membranes. Ca2+ was also distributed throughout the cytoplasmic ground matrix. Much Ca2+ was present in the cell wall soon after its formation during the cell division. Ca2+ was also conspicuous in the vesicles of Golgi in the dermatogen cells. In columella and peripheral cells, there was less Ca2+ in the organelles and cytoplasmic ground matrix, but Ca2+ was present in Golgi vesicles in the peripheral cells. Electron microscopic and X-ray microanalysis showed that Ca2+ was also present in the mucilaginous layer, the outermost cell wall of the peripheral cells.

Centriolar plaque and spindle microtubules in young asci of an ascomycete,Sordaria humana were studied by electron microscopy. Centriolar plaque is electron opaque and has an amorphous structure. Two dispositions of centriolar plaque were observed, one entirely contiguous to the nuclear envelope in a meiotic division and the other partially joined to the envelope in a mitotic division following meiosis. The spindle was formed inside the nuclear envelope and spindle microtubules terminated at the polar protrusion of the nuclear envelope. Some spindle microtubules seem to connect directly with the centriolar plaque passing through perforations of the nuclear envelope.

Studies were made on the fine structure and chemical components of the synaptonemal complex (SC) of pollen mother cells of Tradescantia reflexa. The SC of T. reflexa consists of three partite structures: a central element consisting of two tubules of about 20 nm width, which are twisted together, a lateral element appearing as an electron-opaque line of 25-35 nm width, and transverse filaments of about 10 nm width which connect the central and lateral elements.The central element contains basic protein and a small amount of DNA and RNA. The lateral element contains basic protein and small amounts of DNA and RNA. The transverse filaments contain non-basic protein.

Electron microscopic studies on the substructure of chromatin were carried out using chromosomes in the first meiotic metaphase from pollen mother cells of Tradescantia reflexa. The chromosomes were composed of 300A chromatin threads formed by coiling of 100A chromatin thread. The 100A chromatin threads contained globular structures of about 70A diameter. The location of DNA, protein and RNA were studied by treatment of the chromosomes with DNAase, 0.25N HCl containing 2M NaCl and RNAase.

Cytochemical studies were made on the kinetochore of chromosomes in the first meiotic metaphase and anaphase of pollen mother cells of Tradescantia reflexa. The kinetochore of T. reflexa is ball- or cup-shaped and about 700 nm in diameter. It seems to contain DNA, RNA and basic proteins judging from the effect of uranyle-EDTA treatment, RNase digestion and PTA-staining. The location of these chemical components were also examined.

The course of formation of the stack of annulate lamellae was studied in spermatogonial cells of the grasshopper, Atractomorpha bedeli. A tubular body with a very compact and regular pattern occurs often in the cytoplasm (Fig. 1). Some tubules in the tubular body protrude into the cytoplasm, becoming wider in diameter (Figs. 2 and 3). Protruding tubules may fuse with each other forming a lamella (Figs. 2 and 3). As a result, many parallel cisternae with an annuli or a periodic pattern (Fig. 4) develop in the form of a stack of annulate lamellae. With the further growth of the lamellar stack the compact and regular form of the tubular body is lost (Fig. 6). The tubular body gradually becomes smaller (Figs. 7 and 8), and finally disappears when the lamellar stack has developed fully (Fig. 9).

The behavior of mitochondria was studied in pollen mother cells of Tradiscantia reflexa fixed with OsO4 or KMnO4 under the electron microscope. Mitochondria were found scattered throughout the cytoplasm in cells in prophase I. But with the break down of the nuclear membrane (prometaphase I), mitochondria were found intruded into the nuclear or spindle area. Besides mitochondria, dictyosomes, lipid granules and even plastids were seen in the spindle. Mitochondria in the spindle area or phragmoplast gradually increased in number with the progress of meiotic stages from metaphase I to early telophase I. In mid-telophase I, most of the mitochondria are aggregated about the equator of the phragmoplast. Vesicles were found among the aggregated mitochondria arranged in a series forming the beginning of the cell plate (late telophase I). By the cell plate formed, the mitochondria are distributed evenly between the daughter cells. The relation between the increase in elements of the endoplasmic reticulum at the boundary of the spindle followed by the break down of the nuclear membrane and the intrusion of mitochondria into the spindle is discussed.

The course of formation of the stack of cisternal ER and the tubular ER were studied in successive stages of meiotic divisions in Atractomorpha bedeli.A very few stacks of cisternal ER or tubular ER are seen in the cytoplasm of gonial cells (Fig. 1). In cells in diplotene and diakinesis stages (Fig. 15), however, the cytoplasm is filled with agranular tubular ER. In some cells in early meiotic prophase (leptotene stage), agglomeration of vesicles is seen in the vicinity of Golgi bodies or between Golgi bodies (Figs. 4 and 5). In this region, near to the Golgi body or between Golgi bodies, a developing stack of granular ER cisternae is seen in cells in the pachytene stage (Figs. 7-13). The elements in the ER stack are continuous with the Golgi vesicles. The Golgi vesicles furthest outside the Golgi cisternae are oblong and semi-granular, suggesting that they are half-formed ER cisteranae. In these stages, tubular ER are also seen which are limited to the vicinity of the Golgi body, and continuation of tubular ER with the Golgi vesicles is often observed. These facts suggest that the stack of cisteranl ER and tubular ER are formed by fusion of Golgi vesicles. The stack of cisternal ER afterwards moves in the cytoplasm to a place different from the Golgi region and becomes attached to the nuclear envelope (cf. diakinesis stage, Fig. 14).

The fine structure of centrioles was studied in spermatocytes at prophase of vo species grasshoppers, Acrida turrita and Atractomorplia bedeli. It was found iat the centrioles consist of two equal parts: a proximal half (near the nucleus) is a thickness of 50mμ in width and an electron opaque wall, while a distal half is a thinner (25mμ in width) and less electron opaque wall. The distal half of Le centrioles is surrounded by a granular body which appears to originate from tercellular substance.

The development of the spindle body was studied in the spore mother cells of Equisetum arvense under the electron microscope. The spindle body consists of two elements, spindle fibers and a spindle matrix filling the spaces between these spindle fibers. These spindle fibers originate from the cytoplasm as follows. Microtubules of 25mμ in diameter become visible among the cytoplasmic organelles (such as mitochondria and plastids) in early diakinesis (Fig. 2). These microtubules move to the cytoplasmic region around the nucleus (Figs. 3-6) during diakinesis, while other organelles such as mitochondria and plastids move to the periphery of the cell (forming the clear zone). As soon as the continuous nuclear envelope breaks into fragments (prometaphase-I), these microtubules intrude into the nuclear area from the clear zone together with ER, small vesicles (30-100mμ in diameter) and cytoplasmic matrix (Figs. 7 and 8). They may connect with the kinetochore of each chromosome (chromosomal fibers, Fig. 9). Some microtubules not connected with kinetochore may form continuous fibers running from pole to pole (Figs. 9 and 10).