Stevens. — Spore Formation in Botrychium virginianum . 467 
as its evidence is clear, however, it agrees with the recent conclusions 
of Farmer and Moore, Strasburger, and Gregory. 
Soon after the nuclear thread segments into chromosomes the nuclear 
cavity is seen to be traversed by numerous fine threads which at first take 
on a grey and later a violet colour by the three-colour-method ; the nuclear 
membrane also becomes fibrillar and is stained violet. These characteristics 
become progressively more pronounced and the fibrils begin to press out at 
various points into the cytoplasm in the form of a multipolar spindle 
(Figs. 7, 8, and 9). In this way the nuclear membrane loses its identity 
in the spindle (Figs. 10 to 14 inclusive). In the meantime the cytoplasm 
has become progressively less dense and has evidently contributed of its 
substance to the growth of the spindle. Later the several cones of the 
spindle collect at two opposite poles and fuse, forming the usual bipolar 
spindle (Figs. 15 to 17 inclusive), a polar view of which near the equator 
shows that the fibrils are about equally distributed throughout the space 
occupied by the spindle (Fig. 20). No indications of centrosomes can 
be seen. 
Investigations into the formation of the kinoplasmic spindle have 
revealed two prevailing types. In one type the beginnings of the spindle 
appear first in the cytoplasm, and in the other first in the nucleus before the 
breaking down of the nuclear membrane, or in the nuclear region simul- 
taneously with or just after the disappearance of the membrane. To the 
first type belong Equisetum (Osterhout, ’ 97 ), Liliuni (Mottier, ’ 97 ), Gladio- 
lus (Lawson, ’00), Osmunda (Smith, ’00) Agave (Osterhout, ’ 02 ), Iris, 
Disporum , Aloe , Hesperaloe , Hedera (Lawson, ’ 03 ). To the second type 
belong Cobaea and Passiflora (Williams, ’ 99 ), Lavatera (Byxbee, ’00), and 
Nymphaea alba (Strasburger, ’00). With this second type Botrychium 
virginianum must now be classed. 
There does not, however, appear to be any important significance 
in the existence of these two types. Strasburger (’00, p. 121) suggests that 
they may be due to differences in the amount of extranuclear kinoplasm 
available, and he calls attention to the fact that, as a rule, extranuclear 
kinoplasm takes an important part in the formation of the first spindle 
of pollen-mother-cells, and a subordinate part in the formation of the second 
spindle. It may be also true, it seems to me, that the force which causes 
the differentiation of the spindle emanates from the nucleus, and that 
in some cases this force penetrates the cytoplasm with sufficient energy 
to make itself manifest, and in others it does not. It might well be that 
the second division, following as a rule close upon the heels of the first, and 
with the reduced amount of chromosome material, does not have at its 
disposal sufficient nuclear energy to dominate the cytoplasm, with the result 
that the second spindle is chiefly intranuclear in its origin. 
Evidently cytopolarity (meaning by this term the polarity of the cell 
