48 BOTANICAL GAZETTE [JANUARY 
However, he found that, though the four pollen grains of each 
group usually agreed in size, there were groups in-which two of the 
pollen grains were larger than the corresponding two. This pos- 
sible indication of sex differentiation was destroyed when he found 
a like condition among the pollen grains of hermaphrodite plants 
(Lychnis Flos-jovis, Silene fimbriata). 
In Smilax herbacea no trace of an idiochromosome was found. 
During the metaphase of the first division one frequently found 
a chromosome pair which anticipated the other gemini in separat- 
ing and moving toward the poles (figs. 17, 18), but no differences 
were observed in the homotypic division or in the tetraspores. 
Moreover, precocious chromosome movement away from the 
equator during the heterotypic division has been reported by 
CarviFF (5) in Salomonia, a hermaphrodite: 
For the present, then, we may assume a physiological differ- 
ence in the tetraspores of dioecious plants which has no physical 
manifestation. 
Summary 
1, The nuclei of the young microspore mother cells each con- 
tain several nucleoli of varying size. The nucleoli fuse during the 
prophase, forming one large nucleolus at synapsis. During the 
early prophase the nucleolus is provided with several “papillae.” 
These doubtless represent small nucleolar bodies which also fuse 
with the larger nucleoli. The nucleolus usually has at least one 
papilla until its disappearance at the metaphase. 
2. The chromatin in the young microspore mother cell occurs 
in the form of granules or chromomere aggregates (the chromomere 
is here considered a chromatic unit). 
3. There is no presynaptic reticulum, leptonema, or zygonema. 
The chromatin granules are held in an indefinite linin mesh. 
4. Synapsis is reached by a contraction of the linin-supporting 
structure drawing the chromatin granules together. : 
5. The chromatic elements emerge from synapsis in the form 
of a spireme which soon becomes double. 
6. The spireme shortens and thickens. Transverse segmenta- 
tion of the spireme results in the formation of long paired chromo- 
