430 BOTANICAL GAZETTE [November 



becomes compacted into a tight knot. Soon the six chromosomes, all U-shaped 

 and closely similar, disentangle themselves from this knot and become arranged 

 on the spindle. They split longitudinally, separate, and reorganize the 

 daughter nuclei in the usual way. During the anaphases and telophases the 

 connecting fibers between the chromosome groups increase in number, pull 

 away from the chromosomes, and become thickened at their ends. These 

 thickenings apparently move toward each other and meet in the equatorial 

 region, where by further swelling of the fibers the cell plate is formed. The 

 splitting of the cell plate and the deposition of a wall between its halves were 

 not observed, but are believed to occur. 



In the androcyte mother cells there are a few granules, but nothing which 

 can be certainly identified with the kinetosomes, whose bulk has been dimin- 

 ishing through the generations of androgones. There is, however, in each of 

 them a small "central body" at the center of an aster in the cytoplasm. There 

 is no evidence that it originates within the nucleus. It divides to two which 

 diverge, each with an aster, to opposite sides of the nucleus. Some of the 

 astral rays form cones whose bases are at the nuclear membrane, but between 

 the separating daughter centers there is visible no constant connection. The 

 central bodies are located at the sharp poles of the, spindle, and as the nucleus 

 swells it comes in contact with them. Although they are less conspicuous 

 from this time on, it is reasonably certain that they persist in every instance 

 through mitosis, which is essentially similar to that in the androgones. In the 

 cytoplasm of each androcyte is a deeply staining granule occupying the position 

 of the pole of the former spindle. This is the blepharoplast and is doubtless 

 identical with the central body of the androcyte mother cell. The develop- 

 ment of the spermatozoid is to be taken up in a later paper. 



The spermatogenous cells are marked by a condition of polarity which 

 persists throughout the life of each cell and is transmitted through a long 

 series of cell generations. Except during mitosis, there is no trace of a polar 

 arrangement of the nuclear structures. 



The kinetosomes are believed to be not comparable to " chondriosomes 

 or other non-kinoplasmic inclusions of the cytoplasm. They are not definite 

 morphological entities, but rather unorganized masses of reserve kinoplasm. 

 The definite behavior of the plates in the early androgones is regarded as the 

 result of the presence of a large amount of kinoplasm which tends to occupy 

 a fairly definite position relative to the nucleus. 



In contrast to the kinetosomes the blepharoplast is a definitely organized 

 cell organ, and although the author believes that the question of its morpho- 

 logical nature is still an open one, he inclines toward the view that it is the 

 homologue of a centrosome. This is strongly warranted by the centrosome- 

 like behavior of the blepharoplasts in Polytrickum, with which he ventures to 

 predict other bryophytes will be found to agree. The need of further researches 

 among the Chlorophyceae for light on the origin of the blepharoplast is 

 emphasized. 



