36 Evans . — Branching in the Leafy Hepaticae. 
attachment, some of these modifications representing reversionary tendencies 
and others special adaptations. 
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 modifications 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 the Radula type, and that 
intercalary branches came afterwards. It is possible that this sequence 
appeared independently in different developmental lines. A tendency to 
delay in the process of branch formation was apparently an important 
evolutionary factor. 
There is evidence also that there is a harmonious relation of some sort 
between vigorous vegetative development and terminal branching, and that 
there is usually an antagonism between vigorous growth and intercalary 
branching. 
Literature cited. 
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xc, pp. 213-302, pl. 20-24. 
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geschichte von Radula complanata. Sitzb. der k. Akad. Wissensch. Wien, lxiii 1 , pp. 13-60, 
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(’71 b ) : Ueber die Verzweigung der Lebermoose. Bot. Zeit., xxix, pp. 557-65. 
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