630 'Wisconsin Academy of Sciences, Arts, and Letters. 
vances there is an increase in the proportion of the thicker 
threads in the nucleus. 
The contraction of the thin spirem into the synaptic condi¬ 
tion goes on rapidly after it is once inaugurated so that a single 
anther may often contain the earliest stages of contraction as 
well as nuclei with the chromatin practically at its maximum 
contraction into a tight knot. 
The first perceptible stages of the synatic contraction, as has 
been already mentioned, consist in the drawing together of the 
kinky mass of fine spirem threads to form denser aggregations 
of the threads, at first principally at the periphery of the nucleus. 
This effect of peripheral aggregation seems to be produced by 
the collapsing of the chromatin threads at the periphery. The 
appearance of a withdrawal of material from the central region 
is thus given (Fig. 10). This peripheral collapse is quickly 
followed by a more or less uniform contraction leading to the 
formation of the globular synaptic aggregation at one side of 
the nuclear cavity, the familiar synaptic knot which is figured 
and described in all recent accounts of the reduction divisions 
(Fig. 13). 
The synaptic knot of Smilacina is an especially dense globu¬ 
lar mass lying in contact with the nuclear membrance. Very 
little detail can be made out in the knot itself, but thin tangen¬ 
tial sections show it to be composed of a relatively thick spirem 
which in places can clearly be seen to be composed of tw'o paral¬ 
lel strands. (Figs. 14 and 15). Occasionally strands of the 
spirem project from the synaptic mass and these can usually 
be seen to be double. A! large proportion of the spirem of this 
stage, however, shows this doubling obscurely or not at all. 
There is no orientation of the synaptic knot in any definite 
position in the nuclear cavity as far as I could determine. It 
is located neither in reference to gravity nor to the surrounding 
tapetal layer and the earlier stages of contraction suggest that 
the knot comes to lie on the side of the nucleus to which it is 
most closely attached by linin threads. 
From the relative number of anthers in which the synaptic 
condition is to be found on a given raceme, it is very probable 
