448 BOTANICAL GAZETTE [December 



nucleus, just inside the membrane, there appear chromatin knots 

 which are evidently worked out of the chromatin network by the 

 rearrangement of the material. These chromatin knots, which 

 are continuous with less deeply stained chromatin fibrils, are vari- 

 able in number at first, but gradually the number of chromatin 

 knots becomes definite and they are detached entirely from 

 the chromatin fibrils and become the chromosomes, 24 in number 

 (figs. 19, 54). The chromosomes, after segmentation, gradually 

 assume a slightly elongated rod form and become arranged at the 

 equatorial plate (figs. 20, 55). 



A little before the equatorial plate stage, from the cytoplasm 

 surrounding the nuclear membrane, kinoplasmic accumulations 

 arise at the poles. A well marked centrosome-like structure in the 

 kinoplasmic masses occurs only at the metaphase. The chromo- 

 somes split longitudinally and half of each chromosome proceeds 

 to each pole (figs. 22, 56). During this entire process the spindle 

 is intranuclear. At telophase the nuclear membrane disappears and 

 the two sets of daughter chromosomes, crowded closely together, 

 are surrounded by cytoplasm, and the formation of the nuclear 

 membrane follows (figs. 28, 57). , 



When the daughter nuclei are organized, the central spindle 

 disappears completely (figs. 29, 57). The cytoplasm lying between 

 the two nuclei begins gradually to assume a coarse, irregular, 

 alveolar structure, and the walls of the alveoli, probably after a 

 change in their material, form a new cell plate. Vegetative mitosis 

 is essentially the same in both male and female plants. 



The size of the nucleus varies according to the portion of the 

 thallus in which the nucleus is contained. The hairs and super- 

 ficial cells contain larger nuclei than the huge cells situated below 

 the superficial cells; however, even those in the hairs and superficial 

 cells vary in size. There seems to be no relation between the size 

 of the nucleus and that of the cell. Quite frequently the narrow 

 cells in the hairs contain larger nuclei than the elongated cells; 

 usually the marginal cells in the superficial layer of the thallus have 

 larger nuclei than the others. On the whole, the nuclei of the female 

 plants are slightly larger than those of the male plants. However, 

 such a difference, if it exists, is not very great during the vegetative 



