1899] 
DEVELOPMENT OF THE MICROSPORANGIUM 341 
The transition from the resting stage to the second spindle is 
very abrupt. Two poles are formed in the cytoplasm, which 
move farther apart, so that a bipolar spindle is very quickly 
formed (fig. 77). In the preparations examined, no polar radia- 
tions or multipolar spindles were found. The already distinct 
chromosomes merely move together toward the center in order 
0 form the nuclear plate. Even now most of them retain the 
Vform, and only an occasional one becomes nearly straight. 
They are very irregularly arranged, so that the long arms of 
Some project outward toward the poles, giving a ragged appear- 
ace to the plate, thus distinguishing it immediately from the 
plate formed in the heterotypic division. 
It was found impossible to determine absolutely the nature 
of the segmentation, but from a study of all the stages obtain- 
ible it seems probable that the V is divided transversely. This 
@ course would not mean a transverse division of the original 
ttromosome, if the processes described for the first division are 
he true ones, but rather the completion of a second longitudinal 
‘ltting. No figures were found in any of the spindles that could 
‘interpreted as a case of undoubted longitudinal splitting of 
: Vafter coming on to the nuclear plate of the second spindle. 
: ie other hand, the nearly straight segments moving along 
ee toward the poles are all much shorter than the Vs, but 
ee stely the same diameter instead of narrower, as one 
: expect if longitudinal splitting had taken place. 
* The later Stages are all perfectly normal. The chromosomes 
; | 8¢ themselves in the daughter nuclei and appear at length 
© into a continuous chromatin thread. The nuclear mem- 
‘8° Of the segments to the poles, is much less distinct 
“ring the first division, and it is composed of fewer fibers. 
the = daughter nuclei are formed, a cell-plate is deposited in 
ion ¢ unet- The spindle now disappears and the tetrad 
VOF the pollen-mother-cell nucleus is complete. 
