33 
Evans . — Branching in the Leafy Hepaticae . 
branches are formed. The plants discussed in the present paper, however, 
grew in places where there was an abundant water supply, together with 
the other factors favourable for growth. Apparently, in response to these 
conditions, terminal branches are of frequent occurrence. It would appear 
as if the increased stimulus for growth had acted upon some of the young 
segments in the same way that it acted upon the apical cell of the shoot, 
the result being that new apical cells became differentiated in the segments 
and thus gave rise to new terminal branches. 
In Plagiochila Sullivantii and P. asplenioides the leafy shoots 
represent branches of a prostrate caudex. These shoots continue growing 
for a considerable period but usually remain unbranched. It will be found, 
in fact, that the very conditions which induce a vigorous apical growth and 
terminal branching in Cephalozia bicuspidata tend to inhibit the formation 
of intercalary branches in these species of Plagiochila . It is only when the 
apical growth is diminished or brought to an end, perhaps through the 
enfeeblement or death of the apical region, perhaps through the production 
of archegonia, that intercalary branches can make their appearance. Even 
under these circumstances branching rarely occurs. In his interesting 
researches on regeneration in the Hepaticae, Kreh (’09, p. 249) has recently 
brought out an important fact about P. asplenioides (and certain other 
species). He finds that, when fragments of a shoot are placed under 
favourable conditions, the regenerative branches appear in the axils of the 
leaves, that is, in the position where intercalary branches would normally 
occur. Of course, under these circumstances, the inhibitory action of the 
apical region has been rendered ineffective by direct removal. From these 
various observations it would appear that intercalary branches are not only 
associated with old segments and mature plants, but that the stimulus 
inducing branch-formation of this type must be distinct from the stimulus 
which induces a vigorous growth of the shoot, and therefore distinct also 
from the stimulus which causes terminal branching in such a species as 
Cephalozia bicuspidata. 
Terminal branching in Lophozia is due to stimuli which are apparently 
similar to those indicated in the case of Cephalozia bicuspidata . In 
L. Wenzelii , for example, branches of the Frullania type are not infrequent. 
The plant grows in cold bogs and is therefore under favourable conditions 
for vegetative growth. In the closely related L. alpestris , which grows in 
drier localities, branching is much more unusual. In this connexion Lopho - 
colea heterophylla may also be mentioned. The juvenile condition in this 
species, in which the leaves are uniformly bifid, is often greatly prolonged. 
During this period the conditions favourable for growth are present, and 
terminal branches occur frequently. As the plant approaches maturity 
the shoots develop irregularly lobed or undivided leaves, and finally the 
sexual organs with their bracts. After these changes, associated with repro- 
D 
