244 BOTANICAL GAZETTE [ OCTOBER 
nate. In other cases no such area can be observed, the spindle 
fibers appearing to meet at the centrosome. These bodies, on 
account of their common occurrence at the poles, should perhaps 
retain the name of centrosomes whether they are permanent 
bodies directing cell division or whether they are only temporary 
structures. Whatever these bodies may be they certainly seem 
to be the same in character as the bodies found at the poles of 
cells in animal tissue. They are not only the points to which 
spindle fibers converge, but they are also the centers for a system 
of radiations which pass outward into the cytoplasm. 
H. L. Smith” is perhaps the first to have figured centro- 
somes in plants. He found a small body in diatoms, especially 
in Surirella splendens, which he called the germinal dot. This was 
no doubta centrosome. Guignard™ figured and described these 
bodies in resting cells as well as during karyokinesis. In his 
recent paper’ he finds centrosomes in all phases of nuclear 
division in Nymphea alba. Hé finds multipolar spindles also in 
Nuphar luteum, and says they are very frequent in Limodorum 
abortivus, but he does not give any explanation of their origin. 
In the early part of the telophase the cell wall between 
the two daughter nuclei begins to form. It starts as a gran- 
ular thickening of the middle of the central spindle fibers 
(fig. 26). This thickening gradually extends outward and 
the spindle at the same time gradually increases in diameter 
(figs. 27, 28) until its middle portion touches the cell walls. The 
cell plate then completely divides the daughter cells and the 
spindle soon disappears. In fig. 28 traces of it may still be seen. 
Two centrosomes are now found at each pole, the single ones 
having divided. While the network is being formed the daughter 
nuclei change from an oval to a spherical form, sometimes hav 
ing radiations around them (fig. 29). 
Cotumpsus, O. 
*° A contribution to the life history of Diatomaceze, Proceedings American Society 
of Microscopists 1886 : 1-37 
* Ann. Sci. Nat. (Bot.) VIL. 14: 163-296. 1891. 
* Bot. Gaz. 25: 158-164. 1898. 
