34 
Evans . — Branching in the Leafy Hepaticae, 
duction and the cessation of vegetative growth, have begun to make their 
appearance, terminal branches become very rare. 
In Cephalozia , Lophozia , and Lophocolea the formation of terminal 
branches cannot be looked upon as a firmly established habit. Certain 
species fail to show them at all, and even in species where they may occur 
it is often possible for an individual plant to go through life and produce 
organs of reproduction without being stimulated to develop branches of 
this character. It is very different with such genera as Frullania and 
Lepidozia , where the habit of forming terminal branches is firmly fixed. 
Here the branches arise at fairly definite intervals as long as the conditions 
necessary for ordinary growth are present. Even here, however, there are 
a few facts which point to a slight connexion between vigorous growth and 
branching. In plants growing in dense shade, for example, there are often 
more leaves between successive branches than in plants growing under more 
favourable conditions. In branches, also, the growth of which seems to be 
more or less inhibited by the vigorous development of the main axis, 
branches of a higher order less frequently occur. It is only when such 
branches overcome the inhibitory action and assume the characteristics of 
the main axis that they branch with the same degree of frequency. In the 
first case the conditions unfavourable for growth (and for branching) are 
due to an unfavourable environment, in the second case to correlative 
influences. The second case, however, must not be confused with the one 
described under Plagiochila , where the formation of intercalary branches is 
inhibited by the growth of the branching axis itself, and not by the growth 
of an axis of higher rank. 
The antagonism between apical growth and intercalary branching, 
which is shown so clearly by Plagiochila Sullivantii and P. asplenioides , 
is usually present even in cases where intercalary branching has become 
a characteristic habit. To illustrate this point Cephalozia bicuspidata may 
again be selected. The sexual branches in this species, which are commonly 
intercalary and ventral, make their appearance when a certain degree of 
maturity is reached. Their development, however, is longer deferred in 
vigorous plants, and especially in plants so vigorous that terminal branches 
are present. An important difference between the Cephalozia and the two 
species of Plagiochila in this respect is that the antagonism in the Cephalozia 
is less strong, the result being that the inhibitory influence of the apical 
region is more easily and more regularly overcome. 
The ventral flagelliform branches in Bazzania , which are also inter- 
calary, stand in marked contrast to the branches just considered, although 
the sexual branches in the same genus are apparently dependent upon the 
same conditions as those of Cephalozia bictispidata. These flagelliform 
branches make their appearance only a short distance away from the apical 
region, and there is no evidence that their development is inhibited by 
