258 
ON THE PILOBOT.ID.ZE. 
The columella of Pilaira is somewhat different from that of 
most of the species of Pilobolus. This form of columella is not 
essential to the genus as defined, but it is interesting to notice 
that the same columella is met with in the new species, even 
more markedly than in the two previously described. The chief 
difference arises from the fact that the columella of Pilaira is 
inserted, not at the place where the terminal sphere joins the 
stem, but at a higher level, as it were within the sporange. 
But I think, in order to be consistent, we must regard the 
swollen portion below the columella as belonging to the stem, 
and confine the term “sporange” to the cavity included 
between the columella and the upper hemisphere; though 
there are difficulties in either view. The swelling below, 
which is called the apophysis , is not homologous with the 
swelling of the Pilobolus stem, since it is formed at the same 
time as the sporange. 
The only species of Pilobolus in which a similar columella 
is found is P. nanus. Here also the columella arises within 
the sphere, somewhat above the point of junction with the 
swelling, and thus leaves an apophysis below the sporange. 
It should be remarked that in this species, as in Pilaira, the 
fine acicular crystals of oxalate of lime, which usually encrust 
the sporange, extend even to the apophysis, which would 
seem to show that the latter is in certain respects more 
closely related to the sporange than to the stem. 
It has been already mentioned that the stems of Pilaira 
grow to a considerable height. But the sporange is first 
formed when the stem is short, and is raised afterwards by 
an interstitial growth of the stem, such as is frequently met 
with in Mucor. This interstitial growth takes place chiefly 
in the part immediately below the apophysis, and Brefeld 
suggests, with great probability, that it is the liomologue of 
that process by which the swelling of the stem is produced in 
Pilobolus. 
No clilamydospores, or other asexual modes of repro¬ 
duction besides the sporange, seem to be known in Pilaira, 
but on the other hand we meet here with a sexual repro¬ 
ductive process, such as is known in the Mucors, but has not 
yet been ascertained in Pilobolus. Both Van Tiegliem* and 
Brefeld f obtained these zygotes ; the former cultivated 
them from the spores, thus observing their early development, 
and the latter observed their germination. I will give a short 
abstract of their accounts, although I have not myself met 
* Nouvelles lteclierclies, pp. 57-8, pi. 1, figs. 22-4. 
f Botanische Untersuchungen, iv., 65, pi. 4, figs. 26-8. 
