I2 BOTANICAL GAZETTE [JULY 
Tradescantia, though he formerly thought it resulted from bad fixa- 
tion; and it appears to have been observed also by FARMER and SHOVE 
(10). Morrter states that in these forms there is but little shorten- 
ing of the spirem between synapsis and segmentation into chromo- 
somes. In Oenothera, on the contrary, as is evident from a 
comparison of figs. 15 or 16 with 22, a very considerable amount of 
shortening as well as thickening of the spirem takes place during this 
interval. During the second contraction the paired threads apparently 
fuse, and further shortening of the (from now single) thread results in 
an enormous amount of thickening of the spirem, so that when it uncoils 
from this second contraction it has approximately the thickness of a 
chromosome and exhibits only a few loops. It can then frequently 
be traced through nearly its whole length. At this time there is a 
great amount of variation in the thickness of different parts of the 
spirem, as seen in jigs. 22 and 23. Fig. 19 is a portion of the spirem 
at this period, drawn with a higher magnification. It shows the 
chromatic bodies, which vary in size, imbedded in the linin substra- 
tum. As to how far two different substances are represented, I am 
at present unprepared to say. 
DIAKINESIS 
The single thick thread now segments transversely into 14 chromo- 
somes, the sporophyte or 2x number. At this time there is no indica- 
tion whatever of a longitudinal split in the thread. Even when greatly 
washed out, the material of the chromosomes appears perfectly 
homogeneous, or if a granular structure is observable there is in its 
arrangement no indication of the previous split. At the time of this 
second contraction a pair of chromosomes is frequently observed 
separated from the spirem and apparently always lying with their 
long axes parallel and connected at one end (figs. 20, 22). This 
condition occurs very commonly, although in other cases the spirem 
1s continuous throughout (fig. 21). In no case has more than one 
pair of chromosomes been observed to be thus precociously cut off in 
O. rubrinervis, though two such pairs have been observed in O. lata 
(see I1, fig. 19). In no case has a single chromosome been observed 
to be cut off in this manner, and apparently they are invariably cut 
off in pairs, that is, bivalvent chromosomes are detached. 
