McAllister—Cytology and Embryology. 
627 
these net knots do not differ essentially from the knots them¬ 
selves in their staining qualities, though naturally, from their 
extreme fineness they are much fainter. I think that it would 
be difficult at this stage to demonstrate a difference between 
the two elements of the reticulum by their staining reactions. 
In later stages of mitosis this difference becomes more apparent. 
Here as in the nuclei of the preceding cell generation there is 
no evidence of chromatic aggregations of the nature of prochro¬ 
mosomes, the net knots being too small and too irregular to be 
regarded as such, besides being far in excess of the sporophytic 
chromosome number. 
The reticulum, does not take up a marked peripheral position 
in the nuclear cavity as has been described for a large number 
of plants, though it is clearly less dense in the central region. 
There are also conspicuous clear zones around the larger nu¬ 
cleoli which are practically free from the reticulum. 
The very first stages in synapsis are clearly shown in S. race- 
mosa. The appearance of the first traces of a thin chromatic 
spirem and the first traces of the synaptic contraction are almost 
simultaneous as has been reported for various species by Mot- 
tier, Allen, and others. With low magnification this stage ap¬ 
pears as though the reticulum had drawn together somewhat in 
certain regions, thus increasing the effect of knots by the ap¬ 
parent increase in the size of the chromatin aggregations 
(Fig. 7). At the same time areas are found at the periphery 
which are practically free from the reticulum. In the central 
region also areas are often formed which are nearly free from 
strands and knots. 
High magnification shows in the nuclei at this stage, the pres¬ 
ence of many, fine chromatin threads, much bent and folded on 
themselves in such a way that the appearance of knots is still 
present. Tangential sections of these stages show clearly that 
the apparent knots are due to such bendings and crossings and 
that the chromatin now forms a very fine spirem, which is bent 
and folded in a most tortuous manner (Figs. 7a and 8). 
Neighboring nuclei which with low magnification show little 
difference from the resting nuclei in appearance, show with 
