21 
Evans . — Branching in the Leafy Hepaticae . 
the branching are alike in all respects. Even in Bazzania , where the 
dichotomous appearance is so strongly marked, the branch can at once 
be distinguished from the branching axis by comparing the sequences of 
the leaves. It will be seen in Fig. 27, for example, that the spiral in the 
branch (on the right) is not continuous with that of the main axis below 
the branch, while the spirals in the two portions of the main axis (below 
and above the branch) are continuous. Of course, in such a genus as 
Frullania , the differences between a branching axis and a branch are still 
more striking. 
According to Servit (’07), who accepts Velenovsky’s idea of a dichotomy, 
the genus Bazzania does form two equivalent new axes, and his Fig. 1, 
representing the common B. trilobata , seems to support his assertion. A 
close scrutiny of this figure, however, will show that it is incorrect and that, 
in the axis on the left (the main axis), the leaf on the left-hand side should 
precede and not follow the leaf on the right-hand side. In other words, the 
spirals ought to be homodromous and not antidromous, as the figure 
indicates and as a true dichotomy would require. Servit goes so far as 
to homologize the incomplete leaf in Bazzania (and in other genera showing 
the Frullania type of branching) with the ‘Angularblatt ’ which Velenovsky 
describes in the dichotomous Pteridophytes (’05, p. 249). He states that an 
‘ Angularblatt * is distinguished from other leaves by its form, by its position 
in the angle formed by a dichotomy, and by its being attached equally to 
the two new axes. His characterization applies in all essential respects to 
many Jungermanniaceae with incubous or complicate leaves, but breaks 
down more or less in genera with succubous leaves. In Lophocolea , for 
example, the incomplete leaf is situated below the branch and shows no 
relation to the angle between the branch and the main axis. On the whole 
it seems unnecessary to consider the incomplete leaf as a special morpho- 
logical modification ; it would certainly be simpler to regard its peculiarities 
as due to the restricted portion of the segment which takes part in its 
formation. 
The Microlepidozia Type. 
The condition of homodromy which Bazzania secures through the 
suppression of branching on one side of a branching axis is secured by the 
subgenus Microlepidozia in a different way, an obvious monopodium with 
homodromous branches on both sides being the result. Here, as in Bazzania > 
the branches are restricted to the anodic segment-halves, but while this 
brings them in the ventral segment-halves on one side of a branching axis 
it brings them in the dorsal segment-halves on the other. This remarkable 
peculiarity of Microlepidozia is clearly illustrated by Lepidozia setacea , a 
widely distributed species in northern Europe and North America. In Fig. 28 
a portion of a dextrorse axis with two branches is shown, and it will be 
