r9t1] HAGU E—DIOSPY ROS 4I 
fig. 31, in which a second pair of cotyledons has developed upon 
one of the original pair. 
Microsporangium and pollen 
The studies of the stamens and pollen were made from material 
collected in 1906 from a single tree near Decatur. This tree 
bloomed a few days later than the pistillate trees from which 
collections were being made at the same time. The pollen forma- 
tion was easily traced. The only difficulty encountered was in 
the late stages when the protoplasm is dense and evidently con- 
tains the same chemicals that interfere with the stains in Pus 
embryo sac. 
Each stamen produces four sporangia, whose early stages were 
not traced because the earliest collections were made May 28, 
about a week before the flowers opened. At that date the spo- 
rangia contained large pollen mother cells surrounded by a single 
tapetal layer (fig. 33). The division into tetrads is shown in figs. 
34 and 35. The figures are small and the chromosomes numerous, 
30 at least. In the mature pollen grain more than one nucleus 
could be rarely distinguished, and that one not nearly so conspicu- 
ous as the nucleus of the tetrad (figs. 36, 37). It is very possible 
that the dense protoplasm frequently obscures the second small 
nucleus. A considerable difference in the size of the pollen grains 
was noted; this and the frequent presence of a single nucleus, 
together with the lack of proof of pollination, raise the question 
of the fertility of the pollen. This remains to be determined 
along with the other problems of pollination. 
Summary 
1. The flowers are developed on shoots of the same season’s 
growth. The floral cycles appear in the following order: a pair 
of bracts, the calyx, the corolla and stamens, and lastly the pistil. 
2. The ovule is anatropous and has two integuments. A single 
mother cell is formed beneath the outermost layer of the nucellus, 
from which four megaspores develop, the chalazal one becoming the 
embryo sac. 
