32 BOTANICAL GAZETTE [yULY 
as well as in showing the variation in time of the occurrence of certain 
phenomena due to varying climatic conditions of different seasons. 
It is interesting to note that the different stages of development as 
worked out by Nor&n from material collected in Sweden were, in 
general, from three to four weeks later than corresponding stages in 
the material collected at Wellesley. 
MALE GAMETOPHYTE 
Both J. communis and J. virginiana are dioecious, occasionally 
monoecious. RENNER (21) reported the presence of hermaphrodite 
flowers in J. communis. I searched for similar flowers during the 
period of collection, but was unable to find any. The microsporangia 
were fully developed and the microspore mother cells were already 
present in J. virginiana on March 28, but in J. communis the micro- 
sporangia were not differentiated until April 13. The sporophylls 
are cyclic in arrangement and are disposed in whorls of three, with 
the microsporangia on the under side next to the axis of the cone 
(fig. 1). On April 25 the cells of the archesporial tissue were under- 
going their last division before the formation of the microspore mother 
cells. Following this division, each microsporangium consists of a 
central mass of polygonal microspore mother cells; surrounding these 
is a single layer of tapetal cells, rich in protoplasm and containing 
large nuclei, and a wall of two layers of cells (fig. 2), as has been 
described by other writers. The cells of the outer or superficial 
layer of the wall are large and tabular. They contain considerable 
resin, which causes them to stain diffusely. 
Very soon after the differentiation of the microspore mother cells 
the heterotypic division begins. Lopriore (18) reported that the 
microspore mother cells of Araucaria Bidwillii also undergo a very 
short period of rest before this division is entered upon. As soon as 
the walls are formed about each microspore, the mother wall breaks 
down, setting the spores free in the sporangium. 
The microspores increased in size and were shed May 11. The 
mature pollen grains of Juniperus do not differ as to content from 
