202 
Lang . — On the Sporogonium of Notothylas. 
cally distinct from N. valvata , Sull. He explained the absence of a columella 
as due to the latter sometimes separating into its constituent cells. In the 
following year Milde 1 reinvestigated the genus, and (though his drawings do 
not appear to bear this out) stated that the breaking down of the columella 
took place sooner or later in every case. The work of these earlier investi- 
gators, which was carried out from the systematic standpoint by the 
dissection of dried material, resulted in the recognition of the fact that 
a columella might or might not be demonstrable in the mature capsule of 
any of the species. 
The work of Leitgeb 2 , since it took the development of the sporogonium 
into account, was on another plane, but was hampered by the lack of young 
stages. He had fresh material of N. fertilise and herbarium material of 
N. valvata , melanospora and Breatelii , and confirmed the fact that in nearly 
mature sporogonia of the same species the columella might be present or 
wanting. By extending his observations to the basal region of the capsule, 
where the tissue was still continuous, he showed that the columella was 
really absent, and did not merely dissociate into elater-like cells. When 
present it was often thin and composed of cells similar to the elaters, but 
in other cases was as well differentiated as in capsules of Anthoceros. From 
the study of a few young sporogonia of N, fertilis and N. Bretitelii he came 
to the conclusion that, while the first divisions of the embryo were like 
those of Anthoceros , the central group of cells defined by the first periclinal 
walls gave rise in Notothylas to the sporogenous tissue, within which 
a sterile columella was subsequently differentiated. While he recognized 
the possibility that when the columella was well developed and distinct it 
might have originated as in Anthoceros , he regarded it as unlikely that such 
differences in the laying down of the sporogenous tissue should exist within 
the genus. 
The work of Campbell 3 and Mottier 4 was done on N. orbicularis. The 
capsules were found in all cases to have a well-developed columella, and 
the delimitation of this in the embryo and the origin of the archesporial 
layer from the amphithecium proceeded as in the other Anthocerotaceae. 
Campbell regarded it as unlikely that the other species should differ so 
radically from the one he investigated as would be the case were Leitgeb’s 
surmise correct. 
If the inferences as to the uniform development of the sporogonium 
throughout the genus, made on the one hand by Leitgeb, and on the other 
by Campbell, are put on one side, the observations of the various investi- 
gators are not readily combined into a consistent account of the sporogonium 
of Notothylas . It is clear that a columella developed as in Anthoceros may 
be present, and this is doubtless the origin of the well-defined columella 
1 Bot. Zeit., 1859, p. 33. 
3 Mosses and Ferns, 1st Ed., p. 140. 
2 loc. cit. 
4 Annals of Botany, xxxii, 1894, p. 391. 
