145 
Meiotic Mitoses of Osmunda. 
(Fig. 40) until, as in Fig. 41, long lengths may run parallel to one another, 
and these may be connected by paired beads at intervals At this stage 
the withdrawal of the nuclear contents preparatory to synapsis is first indi- 
cated ; in Fig. 41 the spireme (thread) has retreated from a small area of 
the periphery in the NW. region and in other parts has become slightly 
drawn together. As the spireme (thread) withdraws from the nuclear 
periphery it becomes increasingly thrown into loops, suggesting a continuous 
thread (Fig. 42) ; but it is not possible to prove this supposition. At this 
stage the spireme (thread) resembles a loosely tangled skein of wool with 
threads running very closely parallel (Fig. 44), sometimes actually in contact 
(Fig. 42), whilst others twist and loop over one another (Figs. 42 and 43). 
When the nucleus has passed into the early synaptic stage (Fig. 45) 
the knot, in favourable preparations, is seen to consist of fine threads, the 
cut ends of which appear as small beads of chromatin. The association of 
the sides of the loops (i. e. of two threads) can be recognized towards the 
thinner margins of the knot ; the associations are obscured towards the 
centre by the close tangle of threads. The similarity of the approximating 
sides (threads) is striking (Fig. 46) ; so alike are they that they would be 
regarded as splitting instead of associating had not their origin been traced. 
They also appear exceedingly taut and strained. Both these features will 
again be found to be characteristic of the univalent segments (filaments) of 
spireme when they conjoin in pairs. 
Synapsis. 
The synaptic stage of Osmunda is, as a rule, far more instructive than 
in the majority of plants, where it often happens that its densely staining 
intricate mass makes its structure impossible to resolve. Such is also the 
case in Osmunda when fixed with strong chromic, but with strong Flemming 
and Hermann the individual threads can be clearly seen. Merkel fixative 
has a variable effect ; sometimes it yields a clear, and sometimes a dense, 
appearance during synapsis. 
During synapsis, the association of threads in pairs, prepared for during 
the presynaptic stages , is consummated. The complete sorting out and 
association in pairs, side by side, of the threads of the whole skein of half 
univalent spireme (thread) is achieved, and hence the spireme filament which 
issues from synapsis is, throughout its length, of an entire univalent nature. 
If an early synapsis before association (Fig. 45) be compared with a late 
synapsis after association (Fig. 49), when the spireme (filament) is beginning 
to unravel and to invade the nuclear cavity, it will be observed that the 
difference in thickness of the spiremes is most striking, and that there is no 
difficulty in distinguishing the two phases. The spireme thread, therefore, 
in the early synaptic stages, before association, is not only half the thickness, 
but is also of necessity double the length of the spireme filament of the 
later synaptic stages when association is accomplished. 
