124 Mottier . — Mitosis in the Pollen Mother-cells of 
more essential differences can be followed by those who have not made 
a study of the subject at first hand, but whose work, though along different 
lines, requires a rather clear understanding of the essentials concerning 
which there is much difference of opinion even among those who have been 
extensively engaged in the study of mitotic phenomena. I have also 
abstained from the use of numerous new terms that have crept into cyto- 
logical literature during the past decade, because I believe that much of the 
new terminology is not only not necessary to a clear statement of the 
phenomena, but that a number of the new terms have tended more to confuse 
than to elucidate. 
From the resting nucleus to the hollow spireme. The sporogenous cells 
of Staphylea , at the beginning of the growth period, and after the same has 
fairly begun, form a compact and uniform mass of polygonal cells without 
any intercellular spaces. Fig. 28 is typical of the cells at this stage. The 
large nucleus presents a large number of chromatin granules of varying 
sizes distributed rather uniformly along the periphery, and also within the 
cavity upon a delicate linin network. I say upon a linin net, because I do 
not interpret the delicate and colourless threads connecting the distinctly 
stained granules or collections of granules as merely drawn out threads of 
chromatin substance. Within the cavity of the nucleus is the very large 
nucleolus. The nucleoli in these cells are comparatively free from the small 
bud-like protuberances met with in A. negundo , and in other species of 
Maples. There is not what the writer would regard as the semblance 
of a spireme or spiremes, but only a net. The structure shown in Fig. 28 
passes directly into synapsis. This consists in the collection into a compact 
mass of the network and granules. In Fig. 29 the contraction or balling up 
is going on, the majority of the granules having collected about the nucleolus, 
partly enclosing it. In Fig. 30 we have complete synapsis. In this plant 
the nucleolus is very frequently not included within the mass, but may be 
found entirely outside, and sometimes removed a short distance from the 
mass of chromatin. In sections of anthers at the stage of complete synapsis, 
the large nucleoli lying without the balled-up mass is a very noticeable 
phenomenon when a section of an entire loculus is viewed with low powers. 
Figs. 28, 29, and 30 were drawn from the same section of the same loculus, 
the condition of Fig. 30 prevailing in one end of the anther pocket, and 
that of Fig. 28 in the other. Between the two ends are found all gradations 
from Fig. 28 to Fig. 30. Figs. 28 and 29 belong to neighbouring cells. 
With further progress the contracted mass begins to loosen up, and it 
is seen that a spireme has in the meantime been in the process of formation 
(Fig. 31). As a rule the cell begins to round off when loosening up is 
initiated, as stated for A. negundo , but, as in that plant, there is some varia- 
tion in the time. In Fig. 31 the cell had not rounded off, but other cells 
in the same loculus presented a rounding off at the corners. As the spireme 
