1903] MITOSIS IN PELLIA 47 
2. A centrosphere, but no centrosome, is very prominent 
during early prophases of the first mitosis in the germinating 
spore. The centrosphere is not present at all during the subse- 
quent stages of mitosis. An aster is also conspicuous during the 
early prophases of the first mitosis, but disappears before the 
metaphase is reached. Radiations reappear during telophases. 
The aster is believed to be concerned in separating the poles of 
the spindle; the radiations during the telophase may be con- 
cerned in forming the nuclear membrane or a Hautschicht about 
the nuclear membrane. In the second and third mitoses, the 
centrospheres and asters become more and more indistinct, and in 
succeeding mitoses the centrosphere becomes indistinguishable, 
and a few irregular rays replace the aster. 
3. The rays are believed to be lines of streaming material, 
consisting of the same substance as the centrospheres. 
4. Centrosomes, centrospheres, and blepharoplasts are believed 
to be the same structures historically, being only different mani- 
festations of a common kinoplasmic activity. 
5. No centrosomes or centrospheres were found during mito- 
ses in the apical region of the thallus or in developing antheridia. 
It was not determined whether a blepharoplast occurs toward 
the close of spermatogenesis. 
6. The caps are derived from a Hautschicht surrounding the 
nuclear membrane. The central portion of the spindle is believed 
to be derived in large measure from the nucleolus. 
LITERATURE CITED. 
1. BELAJEFF, W., Zur Kenntniss der Karyokinese bei den Pflanzen. Flora 
79: 430-442. Bls. 72-77. 1894. 
— Ueber die Centrosome in den spermatogenen Zellen. Ber. Deutsch. 
Bot. Gesell. 17: 199-205. A/. 75. 1899. 
3- CAMPBELL, D. H., The structure and development of the mosses and 
ferns. New York. 1895. 
4. CHAMBERLAIN, C. J., Oogenesis in Pinus Laricio. Bot. GAZ. 27 : 268-280. 
bls. 4-6. 1899. 
5. Davis, B. M., Kerntheilung in der Tetrasporenmutterzelle bei Cova//ina 
officinalis L. var. mediterranea. Ber. Deutsch. Bot. Gesell. 16 : 266— 
272. Pls. 16-17. 18098, 
2. 
