Two accounts of microsporogenesis in the genus Lathyrus have been published previously. There are numerous differences of opinion in these two accounts; therefore, a further study of the genus seemed worthwhile. The anther of Lathyrus hirsutus L. is four-loculed when young and two-loculed when fully matured. The tapetum is of the glandular or secretory type and disintegrates before the microspores are mature. It remains uninucleate throughout. Resting microspore mother cells are angular and lie membrane to membrane in a mass with little space between them and the tapetum. Nucleolar budding and fragmentation are apparent during the leptotene stage. The chromosomes form a typical synizetic knot with nucleolar fragments embedded. Only one large nucleolus is observed during zygotene and pachytene. Longitudinal splitting and twisting is apparent during zygotene. A material connection between the chromosomes and the nucleolus is seen. Parasynapsis occurs. Metaphase I is regular, except for an occasional lagging bivalent which apparently reaches the equator and separates normally. Darkstaining granular bodies appear in the cytoplasm. During telophase I a definite nuclear membrane is formed, but the matrix does not completely diffuse from the chromosomes. No cell plate is formed. The granular bodies in the cytoplasm tend to congregate in the equatorial region. At metaphase II the spindles lie at right angles to each other and a tetrahedral arrangement of microspores results. Six spindles can be seen at telophase II. The dark-staining granular bodies in the cytoplasm once again congregate at the equator. Wall formation between the tetrad of microspores occurs simultaneously by furrowing. During division within the microspore an asymmetrical spindle is formed, with a blunt wallward pole and an acute vegetative pole. The generative cell lies against the intine for some time, becoming elliptical. When it later moves away from the wall, it assumes a spherical shape. The mature pollen grain has three germ pores.
The cytology of Cylindrocapsa scytonemoides has been investigated. The chromosome number is 36. Out of these one of the chromosomes, is considerably longer (2.5μ) in comparison with the rest. The septum initiation takes place in telophase which is unlike the one reported in C. involuta. The nuclear behaviour and the morphology of the chromosomes are in general agreement with those of the other members of the Ulotrichales so far studied. Further the germlings of this alga have attaching discs which are similar to Uronema. In view of these findings the systematic position of the alga has been discussed.
The process of fertilization and the course of early cleavages in the cross between the dog-salmon (Oncorhynchus keta) and the pink-salmon (Oncorhynchus gorbuscha), and in its reciprocal cross were found to proceed in normal manner. There occurred no di- and poly-spermic condition in insemination. The behavior of chromosomes during early cleavage of the hybrid egg showed nothing unusual. There was no lag or elimination of any chromosomes. There is no evidence to show that the spermatozoa acted as a parthenogenetic agent.
1. Cytological investigations on 8 species of Selaginella (including an unidentified species) indigenous to South India were conducted. The chromosome numbers in the species studied are as follows: S. gracilis (n=10 and 2n=20), S. wallichii (n=10 and 2n=20), S. braunii (n=10), S. plana (n=10 and 2n=20), S. crassipes (n=9), S. involvens (n=9), S. willdenovii (n=9 and 2n=18), Selaginella sp. (unidentified) (n=18 and 2n=36). 2. All the species studied except the unidentified species are diploids on basic number 9 or 10. The unidentified species is a tetraploid based on the number 9. 3. Aneuploid change of chromosome number (from 10 to 9 as observed in this study), hybridization followed by chromosome doubling, and probably accumulation of intrachromosomal changes have been suggested to be operative in speciation of the genus Selaginella.
The karyotypes of the following 9 species of Phalaenopsis (Orchidaceae) were analyzed: P. amabilis var. grandiflora, P. schilleriana, P. lindeniiP. equestris, P. luddemanniana, P. luddemanniana var. ochracea. P. boxallii, P. mannii, P. violacea, and P. pulcherrima (Dorites pulcherrima). The first 6 species, which are native to the Philippines, had small chromosomes and relatively symmetrical karyotypes. There were recognizable differences in karyotypes among the species belonging to different sections. The latter three extra-Philippine species had chromosomes that were 2 to 3 times larger than those of the Philippine species. Their karyotypes were less symmetrical with a larger number of sub-terminal chromosomes, and/or with larger differences in size between chromosomes of the same set. On the basis of karyotypes, some aspects of taxonomy and evolution of Phalaenopsis were discussed.
1. The results of the cytological investigations in the endosperm of Amaryllis belladonna L. have been reported. 2. The endosperm was free nuclear up to 17-18 days after pollination and then became cellular. 3. The endosperm showed, especially at the free nuclear stage, a significant disparity in the size of its nuclei. The ranges in length and breadth of nuclei in 18 day old endosperm were 27.28 to 153.00 microns and 20.40 to 68.00 microns, respectively. 4. Endopolyploidy, aneuploidy, multipolarity of spindles, chromosomal bridges and nuclear fusions were responsible for the variation present in the size and shape of endosperm nuclei. 5. The normal cytological constitution of the endosperm was determined as triploid with 3n=33 chromosomes. 6. A study of the nucleolar numbers and chromosome counts of the endosperm and root tip nuclei has revealed that the number of nucleoli per nucleus cannot be used as an indicator of polyploidy in Amaryllis belladonna. 7. Breakdown of the endosperm was possibly caused by the cumulative effect of mitotic aberrations which were apparent in the form of bridges, multipolarity of spindles, polyploidy and aneuploidy. The frequency of the occurrence of mitotic abnormalities was found to be significantly higher in the collapsing endosperm.
Electron microscope studies of tips of aerial roots of Chlorophytum capense (L.) Kuntze showed the formation in the nucleus of a large number of invaginations, in which mitchondria accumulate. These mitochondria are seen in many cases attached to the nuclear membrane, which appears destroyed at the point of attachment, as if the mitochondrion were exchanging some substances with the nucleus or were being absorbed by the nucleus. This phenomenon can conceivably be a mechanism to transfer ATP and possibly other substances from the mitochondria to the nucleus.
Graphs were obtained of granular motion in Amoeba proteus by the pictograph technique which records the motion exhibited by granules, illuminated by darkfield microscopy, in a single time exposure photograph. The pictographs are made by the organism and are accurate but complex recordings. Information obtained from this method demonstrates that the plasmagel tube is capable of contraction. However, there is no significant change in morphology of this organism during its locomotion. Importance is placed on the active acceleration of plasmasol from the interstices of the tail's Plasmagel. It is suggested that this might be the basic “contractile” event of amoeboid locomotion which supports the concept advanced by Kamiya for Physarum that an active sliding of plasmasol on plasmagel is a fundamental requirement of protoplasmic motion.
A study was made of the effects of postirradiation protein synthesis upon u.v. inductions of cytoplasmically inherited respiratory deficiency and genic reversions from adenine auxotrophy to prototrophy in Saccharomyces. Conditions affecting protein synthesis were modified by (a) varying the nutritional status of cells before and after irrradiation and by (b) use of the phenylalanine analogue, p-fluorophenylalanine. Circumstances favoring protein synthesis during the first half of the first postirradiation cell division were found essential for the induction of a maximal number of genic mutants. Previous investigators have reported similar findings with bacteria and Neurospora. Postirradiation protein synthesis did not affect the frequency with which cytoplasmic mutants were induced. These results provide additional support for the proposition that u.v. induced gene mutation is an indirect process requiring the translation of primary radiation damage into the genetic apparatus through processes involving protein synthesis. They also suggest that cytoplasmically inherited respiratory deficiency may be induced by a direct derangement by u.v. of the structural integrity of the mitochondrion.