430 BOTANICAL. GAZETTE [JUNE 
mitoses in growing regions of the tetrasporic plant show that the 
nuclei have 40 chromosomes (the sporophyte number), while it will 
be remembered that the nuclei of the sexual plants have 20. 
I shall not enter at this time into a detailed description of the events 
which take place during the formation of the tetraspore mother-cell; 
the only thing to be remembered is that the number of the chromo- 
somes appearing during this mitosis is 40,so that it follows that the 
nucleus of the tetraspore mother-cell contains 40 chromosomes. 
The nucleus of the tetraspore mother-cell increases somewhat in 
size, accompanied by the growth of the cell itself; yet the latter is 
relatively slow until just before the first mitosis of the nucleus, but 
very rapid after that. 
The resting nucleus of the tetraspore mother-cell contains a fine 
network of linin in which the chromatin is distributed irregularly in 
larger and smaller granules. The nucleolus has no visible connection 
with the linin thread. With the further growth of the nucleus the 
linin thread increases in thickness; in such an irregular way, however, 
that in some parts the threads are uniform in thickness and in the 
others they appear to have knots. The chromatin thread now forms 
a fairly well-developed spirem. 
This condition presently passes into the so-called stage of synapsis, 
when the spirem consists visibly of two parallel threads close together, 
while in the other parts the two are in contact side by side or fused 
into a single thread. The two threads may represent, according to 
recent interpretations of synapsis, chromatin of maternal and paternal 
origin. 
After synapsis, the tangled thread becomes distributed throughout 
the cavity of the nucleus. The spirem now shows the longitudinal 
fission which precedes the separation of chromatin granules into two 
sets, and then the spirem segments into 20 chromosomes, each show- 
ing clearly its bivalent nature. : 
While this process of chromosome formation is going on in the in- 
terior of the nucleus, the kinoplasmic material surrounding the nucleus 
becomes concentrated at two poles of a spindle, and when the chrc mall 
somes are arranged in the equatorial plate a minute body cccuples 
the center of each pole. The body might be called a centrcsome, 
but it has not been possible to recognize its presence during prophase 
or to follow it after anaphase. 
