1899] DEVELOPMENT OF THE MICROSPORANGIUM 359 
Fic. 23. The microspore before the division of the primary nucleus. 
Fig. 24. Same after the generative cell has been cut off ; the generative 
wucleus is very dense. 
PLATE XXV. Potamogeton foltosus Raf. 
| Fic. 25. The row of cells derived from the primary hypodermal cell at 
} ach corner of the young anther. 
Fig. 26. A portion of the anther wall in a later stage; the outer layer is 
the epidermis, the second becomes the endothecium, the third disintegrates, 
the fourth is the tapetum, and farther inside are some archesporial cells. 
Fig. 27, The structure of the mature anther wall; the endothecium with 
isindistinctly spiral markings is limited on the outside by the epidermis, and 
mithin bythe disintegrated wall-cells and tapetum. 
Fig. 28. An archesporial nucleus in the resting stage; the indistinct 
{nin network contains a few pale-staining chromatin granules ; the large dark 
ass is the nucleolar-like body ; and the black bud at the side is possibly the 
tucleolus, 
Fig. 29, Synapsis; there is very little chromatin in the contracted mass. 
‘Fig, 30. Later stage of synapsis; granules are expelled and the linin is 
‘ginning to spread out. 
Fig. 31. The spirem; contains very little true chromatin. 
la The nucleolar body has disappeared and at the same time the 
€s were formed ; the membrane is here spreading out. 
Fig. 33. The multipolar spindle and chromosomes. 
Fig. 34. Same becoming bipolar. 
Ube 35. The bipolar spindle and nuclear plate; the chromosomes ase 
be double, 
Fig. 36. Daughter nuclei after the first division; the chromosomes 
“ain distinct, ; 
- The second or reducing division, nuclear plate stage 
- Same showing the daughter segments moving toward the poles. 
- The reducing division ; chromosomes in the nuclear plate. 
A microspore with its primary nucleus. 
- Same showing the mitotic division of this nucleus. 
me .. with a free vegetative nucleus, and a small dense genera- 
oe ed by a convex wall. 
: 43. Same showing the division of the generative nucleus. 
IG, : 
Sie A mature microspore in which the two dense€ sperm nuclei ar€ 
| sed by a cell wall. | 
