Stevens. — Spore Formation in Botrychium virginianum. 469 
In the fact that the daughter-nuclei resulting from the first division 
pass through a resting-stage, Botrychium differs from Pteris as reported by 
Calkins (’ 97 ), and Scolopendrium as described by myself (’ 98 ). According 
to Calkins, in Pteris , when the chromosomes of the first division have 
arrived at the poles they again divide and pass through the stages of the 
second division without having fused with each other. In Scolopendrium 
I found that the chromosomes of the first division fuse together after they 
have arrived at the poles, and form a thick thread, but that no other steps 
towards the formation of a resting-nucleus are taken. 
The processes of the second division do not seem to differ essentially 
from those of the first so far as concerns the formation of the spindle. The 
thread of the reticulum thickens and the reticulum loses its netted character 
(Fig. 29 ) ; the chromatin gathers together in clumps (Fig. 30) ; the nucleoli 
disappear, and the nascent spindle becomes visible within the nuclear cavity, 
and finally presses outwards in the form of a multipolar spindle (Figs. 31-2). 
These prophases evidently come rapidly to completion, for they are not 
frequently found, even in preparations in which all other phases abound. 
The manner of the separation of the chromosomes in the second division 
I have found it impossible to determine (see Figs. 30 to 36 inclusive). 
In the second division the daughter-nuclei may divide in the same 
plane or in planes at right angles to each other (Figs. 33 to 36 inclusive). 
In either case, soon after the chromosomes have arrived at the poles, 
and before the resting granddaughter-nuclei have been formed, the thick 
plate of cytoplasm which was laid down in the equator of the first division 
becomes gradually transformed into kinoplasmic connecting fibres (Figs. 37 
to 41 inclusive). If the planes of division are at right angles to each other 
the fibres connect the granddaughter-nuclei as shown in Figs. 37 to 40 ; 
but if both nuclei divide in the same plane the granddaughter-nuclei become 
joined by the connecting fibres as shown in Fig. 41. Fig. 37 represents 
a slightly later stage than Fig. 36. At a in Fig. 37 is the bundle of con- 
necting fibres remaining at the close of the anaphase of the second division, 
while at b and b are nascent connecting fibres arising out of the dense cyto- 
plasm laid down in the equatorial region at the close of the first division, as 
in Fig. 28. These may be called secondary connecting fibres to distinguish 
them from the primary connecting fibres at a . Both primary and secondary 
connecting fibres take part in the formation of the cell-plates that are 
to demark the spores, as is clearly shown in Fig. 41, where both of the last 
nuclear divisions took place in the same plane. Figs. 40 to 44 inclusive 
show a progression of events in the formation of the cell-plates, with 
attendant changes in the condition of the cytoplasm. Reviewing the 
stages thus far described we find a striking confirmation of the opinion 
of Strasburger (’ 97 ) that the trophoplasm and kinoplasm are mutually 
interdependent, one increasing at the expense of the other as the require- 
