Cannon: StupiEs In PLANT Hyprips 163 
as will be spoken of again in this paper. The withdrawal of the 
cytoplasm is to be regarded as the normal and regular occurrence 
in the archesporial cells of cotton, and is not therefore analo- 
gous to the condition observed by Juel in Syrimga * where it was 
an indication of degeneration. 
About the time of the formation of the spore mother-cells, and 
as a regular structural change accompanying it, the cytoplasm of 
the normal cells shows a marked change in its structure. A zone 
of dense protoplasm which takes the cytoplasmic stain with avidity, 
is formed around the nucleus in contact with the nuclear wall. 
This perinuclear zone is found also in the developing pollen grains 
of various plants of pure descent.+ It is seen not only in the 
cytoplasm of the spore mother-cell, but in the later stages as well, 
even in the young tetrads as in Lavatera.t The structure of the 
zone appears to be granular, although in some preparations and 
under comparatively powerful magnification—Zeiss ocular 18, 
apochromatic oil-immersion 2-mm. objective—it seemed reticular, 
thus resembling Zarix.§ Outside of the perinuclear zone is the 
main portion of the cytoplasm which is alveolar in structure and 
in addition to these two sorts of protoplasm a layer of fibrillae 
midway between the periphery of the cell and the perinuclear zone 
is also occasionally found in the spore mother-cells. When first 
observed the fibrillar layer is of a rather loose structure, but in the 
older cells the fibrillae are closely bound together and form a 
compact zone. 
A similar zone is figured by Mottier for Zidiwm. || This filar 
plasm, like the achromatic figure, takes the gentian-violet with 
Flemming’s triple stain. As a rule the spore-mother cells do 
not contain this structure, but it is found with great regularity in 
the cytoplasm of the older cells. The genesis of the fibrillar layer 
is difficult to account for in the spore mother-cells ; in the later 
stages of development, however, it is formed by the mantle fibers 
* Juel, 7. c. 640. 
t Lloyd. Mem. Torrey Club, 8: 71. 1902. — 
t Byxbee. The Development of the Karyokinetic Spindle in th 
Cells of Lavatera. Proc. Calif. Acad. Bot. III, 2: 63. 1900. oe 
2 Belajeff, Zur Kenntniss der Karyokinese bei den Pflanzen. Flora, 79: 430. 
1894. 
e Pollen-Mother- 
Mottier, Beitrage zur Kenntniss der Kerntheilung in den Pollenmutterzellen 
etc. Jahrb. Wiss. Bot. 30: /. 7. 7.5. 1897- 
