TETRAD AND EMBRYO-sac MITOSES 71 
When, however, the true apex of the spindle does not insert 
itself immediately in the ectoplasm, one may usually discover a fine 
strand of kinoplasm extending from the apex of the spindle to the 
ectoplasm (/. 9, fig. ro). 
In further support of the view that the spindle often stands in 
some intimate relation with the ectoplasm I may cite the instance 
from which fig. 4 of Pl. و‎ was taken. The axis is here oblique to 
the optical plane, and one pole is seen to end distinctly at a point 
from which extend fibers in a somewhat radial fashion. Careful 
examination revealed the fact that the radially placed fibers lay in 
the peripheral layer of the cytoplasm, that is in the ectoplasm, and 
the latter therefore appears to bear a distinct mechanical relation 
to the spindle. 
In many cases in which the dimensions of the cell are much 
greater relatively to the size of the spindle such attachments have 
not been found. This lack is especially obvious in the large 
embryo-sac-mother-cell of Crucianella, in which, however, as in 
the pollen spindles, extra-nuclear “supporting fibers " may be ob- 
served to run out from the spindle apices to the ectoplasm in the 
direction of the equator (pl. rz, figs. 16, 77). Similar conditions 
prevail in the pollen mother-cell in Crucianella macrostachya 
(pl. 11, fig. 35), where but a single row of sporogenous cells 
occurs in each locule of the anther, The cells are relatively large 
and the mitotic figure in both the first and second divisions lies 
freely in the cytoplasm. In this instance neither the insertion of 
the spindle poles, nor of the extra-nuclear supporting fibers in the 
ectoplasm could be seen with certainty. Indeed the orientation 
of the spindle fibers during the second division is often such as to 
preclude the possibility of the insertion of one of the poles at least, 
as will be seen in p/. rz, fig. 35, which shows that the axes of 
the two spindles lay in the same plane at right angles to each 
other; unless, indeed, we may expect to find the pole of one 
spindle passing through the body of the other. _ 
In the developing pollen in many plants a distinct zone of 
very granular cytoplasm has been described by Juel,* Lawson, f 
2. Bie Kaenthellungen | in den Pollenmutterzellen von Ferien diti fulva und die 
bei denselben auftretenden Unregemässigkeiten. Jahrb. wiss. Bot. 30: 204. 189 
Some observations on the Development of the Karyokinetic — in the 
Pollen mother-cells of Cobaca scandens. Proc. Cal. Acad. Botany, III. 1 : 899. 
