Nichols, A morphological study of Juniperus communis var. clepressa. 205 
a pairing of the chromatic material is present in the nucleus of 
the resting mother cell of tlie form under consideration the writer 
is nnable to make it out. Nor is it possible to recognize in the 
nucleus, either at this time or during the subsequent stages leading 
up to the formation of microspores, a sharp distinction between 
chromatin and linin, such as is present in the nucleus of the body 
cell just before its division. In view, however, of the small size 
of these nuclei this fact by no means precludes the probability that 
such a differentiation may be present. 
One or more large nucleoli are conspicuous in the nucleus. 
The cytoplasm is uniformly distributed through the cell, and in 
most cases presents merely a granulär appearance; but in well 
prepared. sections a distinct alveolar structure is evident, the contour 
of the non-staining “alveolar spheres” being outlined by the thickly 
scattered microsomes (see Wilson 1900, p. 46). Minute, glistening 
granules of starch are present in the cytoplasm, and these are 
more or less prominent during the succeeding stages of development. 
Tetrad division. — The behavior of the chromatic material 
in the nuclei of the microspore mother cells during the early pro- 
phase of the heterotypic division is very similar to that described 
by Allen (1905) in the pollen mother cells of Lilimn ccinadense. 
As the nucleus approaches synapsis the finer threads of the chro¬ 
matic network are drawn in, the material of the knots shows a ten- 
dency to become distributed along the coarser connecting strands, 
and the reticular structure gradually gives way to a series of more 
or less united, lumpy bands. At the same time it becomes evident, 
as shown in figs. 16 and 17, that in many places separate strands 
or masses of chromatin have come to lie alongside one another. 
Sometimes they approach so close that they appear to have united, 
but again it can be made out that there are two distinct strands 
lying side by side. Coincident with these changes the chromatin 
begins to aggregate toward the central region of the nucleus, and 
a heaping up of the nuclear materials begins. This continues until 
a mass of tightly interwoven strands is formed which moves to one 
side of the nuclear cavity and assumes a Position close to the nuclear 
membrane (fig. 18). Just what conditions prevail during synapsis 
it is impossible to make out with certainty. Occasionally, however, 
threads are found which project out from the almost homogeneous 
mass, and from the appearance of these, and in view of the pre- 
ceeding and subsequent phenomena, it may be inferred that there 
is present at first a series of double threads, and that toward the 
close of synapsis these coalesce and unite end to end to form a 
single bivalent spirem. There appears to be no rule as to which 
side of the nuclear cavity the synaptic mass occupies (fig. 10). 
The nucleoli in most cases protrude from the chromatic ball and 
occasionally are entirely extruded, but they never exhibit the 
flattened appearance described by Allen (1905). 
Considerable theoretical interest is attached to the view held 
by several eminent cytologists, among them Berghs (1904, 1905), 
Allen (1905), and Overton (1905), that there is a presynaptic 
