132 BOTANICAL GAZETTE [FEBRUARY 
runs a well defined vascular bundle. The whole anther is invested 
by a layer of epidermal cells whose outer surface is somewhat 
thickened. In the interior of each microsporangium is a mass of 
thin-walled sporogenous cells (usually fifteen to twenty), indicating 
that the archesporial cells have developed some time before. These 
are surrounded by a well-defined tapetal layer. The four micro- 
sporangia are borne on the ventral surface of the stamen. 
During the latter part of February and the first week in March 
the anthers increase greatly in diameter. This increase does not 
take place in the length of the connective so much as in the size of 
the four microsporangia. The connective appears to have reached 
its full development earlier. The growth of the microsporangia is 
accompanied by rapid increase in the number of sporogenous cells. 
While in a resting condition, the sporogenous cells differ from the 
surrounding cells in their greater size, in their generally hexagonal 
shape, and in the fact that the nucleus is larger in proportion to the 
size of the cell and shows a more distinct chromatin network than 
does the nucleus of the vegetative cell. Division of the sporogenous 
cells continues until they form, taken together, two-thirds of the 
diameter of the microsporangium. The last cells formed are con- 
siderably larger than those formed in the earlier stages of the 
process, 
While this is going on, the filaments begin to lengthen out and 
push the anthers up until they press against the infolded edges of 
the perianth. By the second or third week in March the divisions 
of the sporogenous cells are completed. The mature pollen mother 
cells thus formed are from one and a half to two times the size of the 
cells from which they have descended. The tetrad formation is as 
usual, The walls of the spores are greatly thickened and do not 
stain readily with any of the anilin stains.2 The cytoplasm is granu- 
lar and the nucleus ill-defined. From the difficulty experienced in 
finding material in this stage of development, it is evident that it is 
very evanescent. 
An examination of the pollen grains in water shows that the exine 
? Staining the tetrads with haematoxylin was not attempted. Sections fixed in 
picric acid and stained with eosin showed the fibrous portion of the anther stained 
bright orange, mature pollen grains deep red, tetrads light yellow. 
