5] Anatomie, Morphologie, Biologie, Teratologie. 35 



12. Evans, A. W. Branching in the leafy Hepaticae. (Ann. of Bot., 

 XXVI, 1912, p. 1—37, 36 fig.) 



Verf. gibt folgendes Resümee: 



Two distinct kinds of branching, terminal and intercalary, may by 

 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, characteristized 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 Fndlania type 

 the branch represents the ventral half of a lateral segment; in the Microlepi- 

 dozia type, the dorsal half of a lateral segment; in the Acromastigum 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 one incomplete leaf, which represents the other half of 

 the same segment; in the Radula type the branch is accompanied by a com- 

 plete leaf, which belongs to the same segment. 



In the Frullania 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 the kathodic 

 segment-halves. 



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-handside (when 

 the shoot is viewed from the ventral surface), but subfloral innovations in the 

 Lejeuneae sometimes show variations. 



The leaves at the b;ise of a terminal branch, especially one of the 

 Frullania type, are more or less modified in form, in size, and in manner of 

 attachment, some of these modifications representing reversionary tendencies 

 and other special adaptions. 



Intercalary branches may be either lateral or ventral in position. Their 

 spirals show little or no relation to the Spiral of the branching axis, and there 

 is nothing definite about the position of the first branch-segment. The modi- 

 fications at the base of a branch are reversionary in character. 



There is some evidence (derived from phylogenetic and ontogenetic 

 considerations) that the Frullania type of branching was the first one to 

 make its appearance, that this was followed by Radula type, and that inter- 

 calary branches came afterwards. It is possible that this sequence appeared 



3' 



