35 
Evans. — Branching in the Leafy Hepaticae. 
apical growth. In fact the stimulus which induces growth and the stimulus 
which induces branches of this character apparently act in harmony. From 
the consideration of this peculiar case, therefore, it seems very probable that 
the stimuli inducing intercalary branching are not always identical. 
Summary. 
Two distinct kinds of branching, terminal and intercalary, may be 
distinguished in the Jungermanniaceae. In terminal branching the branches 
arise in very young segments ; in intercalary branching they arise in 
segments which are more or less mature. 
Terminal branching includes four distinct types, characterized by the 
portion of the segment which takes part in branch formation. These four 
types are here designated the Frullania type, the Microlepidozia type, the 
Acromastigum type, and the Radula type, respectively. In the Frullania 
type the branch represents the ventral half of a lateral segment ; in the 
Microlepidozia type, the dorsal half of a lateral segment ; in the Aero - 
mastigum type, one of the halves of a ventral segment ; in the Radula type, 
a portion only of the ventral half of a lateral segment. 
In the Frullania , Microlepidozia , and Acromastigum types the branch 
is always accompanied by an incomplete leaf, which represents the other 
half of the same segment ; in the Radida type the branch is accompanied 
by a complete leaf, which belongs to the same segment. 
In the Frtdlania type the first branch-segment is ventral, and usually 
gives rise to an underleaf, the second segment is acroscopic (with respect to 
the branching axis) and gives rise to the first lateral leaf, while the third 
segment gives rise to the second lateral leaf, basiscopic in position. The 
branch-spiral is homodromous with the axis when the branch has arisen in 
an anodic segment-half, and antidromous when it has arisen in a kathodic 
segment-half. 
In the Microlepidozia type the third branch-segment is ventral in 
position, and the branch-spiral is always homodromous with the axis because 
the branches of this type always arise in anodic segment-halves. 
In the Acromastigum type the third branch-segment is ventral (just as 
in the Microlepidozia type), and the branch-spiral is homodromous or 
antidromous with the axis, according to whether the branch is situated 
in the anodic or the kathodic segment-half. 
In the Radula type the first branch-segment is sometimes ventral, 
but usually lateral and basiscopic. The branch-spiral is usually sinistrorse 
on the left-hand side of a branching axis, and dextrorse on the right-hand 
side (when the shoot is viewed from the ventral surface), but subfloral 
innovations in the Lejeuneae sometimes show variations. 
The leaves at the base of a terminal branch, especially one of the 
Frtdlania type, are more or less modified in form, in size, and in manner of 
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