1900 ] THE CELL PLATE IN HIGHER PLANTS 93 
differentiated into three zones (fig. 2), as Went first pointed out 
in other forms. But I cannot confirm the statement that the 
darker subnuclear zones take their characteristic appearance from 
a stainable ground substance between the spindle fibers. A care- 
ful study of the preparation from which fig. 2 was taken has 
convinced me that the darker portions are due to the structure 
and arrangement of the spindle fibers themselves. Some of the 
- fibers are undoubtedly thicker in this region than in the equator 
(fig. 27,a). With this differentiation in structure is combined 
the fact that the bundles have here begun to separate into single 
fibers (fig. 2). The two processes taken together account for 
the extra density observed. The above facts seem to me to 
indicate that the kinoplasmic activity preparatory to the forma- 
tion of the cel] plate begins in the region of the nuclei. The 
thickened appearance of the fibers soon extends throughout their 
length (figs. 3 and 27, 6). Concurrent with such thickening the 
Separation of the bundles into single fibers continues until the 
central spindle has the same appearance throughout. By com- 
paring figs. 2 and 3 it can be seen that nearly all of the connect- 
ing fibers have apparently shortened slightly, leaving clear 
Spaces just under the two daughter nuclei. In many cells there 
were often observed single connecting fibers in which the above 
described changes did not seem to be taking place, but they 
were never numerous in any one cell. Their distribution was 
not regular, They were as often seen in the central as in the 
more peripheral parts of the spindle. I shall have occasion to 
refer to them in the description of later stages. Granules of 
‘rophoplasm may often be detected among the ends of the con- 
necting fibers at this Stage. These have probably flowed in as the 
fibers contracted. The process of separation of the fibers described 
above Sives the appearance of an increase in the number of spindle 
hp Whether such an increase actually occurs is doubtful. 
€ larch the evidence, so far as I have observed it, seems to 
roti the apparent increase is due entirely to the above men- 
Processes. In this connection the hypothesis lately sug- 
8ested by Strasburger, that the spindle fibers are increased in 
