1900] DEVELOPMENT OF THE POLLEN GRAIN 93 
concerning the cell division. Invariably a cell plate separates 
the daughter nuclei, and the concave side of the forming mem- 
brane is toward the small, generative nucleus (fig. 72). Gener- 
ally the generative cell is cut off by a distinct wall, and in the 
pollen grain two principal types of generative cells are seen. 
In the first place, the strongly convex membrane necessitates 
the formation of an oval cell, and the large vegetative cell 
grows closely around it. The smaller cell is, as it were, drawn 
into the protoplasm of the surrounding cell, and thus the 
former becomes more nearly spherical in outline. The generative 
cell at first contains considerable cytoplasm, but this is gradu- 
ally lost, although the shrunken wall remains, as in jig. 13. 
Whether taken into the protoplasm or not, the space between 
the walls of the vegetative and generative cells is evident, and 
remains surrounding the generative cell as a distinct court. On 
the other hand, the generative cell may remain closely adherent 
to the wall for some time, and in this case it is sometimes oval, 
but usually distinctly fusiform or lens-shaped, sooner or later. 
The fusiform cell usually remains attached until germination of 
the pollen grain. As before, the cytoplasm largely disappears, 
and there remain only small courts on each side of the oblong 
nucleus. In some cases the nucleus itself becomes fusiform, 
and it is difficult to distinguish the enveloping walls. 
In the division of the microspore nucleus in Peltandra, the 
Spirem ribbon is longer and more complicated than in Symplocar- 
pus; and on segmentation the chromosomes are longer. As the 
daughter segments pass to the pole, they are distinctly U or V- 
shaped, as in fig. 24. The spindle is formed much as in Sym- 
plocarpus, being somewhat multipolar at the pole which is in 
contact with the wall layer; and at the free pole the apices do 
ta converge, as shown in fig. 23. In Peltandra, more- 
ents ae puch an open question as to the influences deter- 
‘ Wom . position of the nucleus in the mature RISE TUSPOTe. 
La. occupies much es the contents of the micro- 
us ne rae 1s seems to be an efficient means for the orientation 
cus in such a position that one pole of the spindle 
