24 
Evans.- — Branching in the Leafy Hepaticae. 
The Radula Type. 
The Radula type of terminal branching was the one # first described 
by Leitgeb (’71 a) and has already been briefly characterized. It has some- 
times been referred to as the ‘ Lejeunea type’ by the writer (’07, ’08). On 
account of the late differentiation of the apical cell of a branch, the leaf 
belonging to the same segment is normally developed and shows none of 
the interesting peculiarities described under the previous types of terminal 
branching. As Leitgeb points out, a branch of the Radida type always 
arises in a cortical cell adjacent to the base of a leaf on the basiscopic side 
and in the ventral portion of the segment. In the genus Radula the 
branches all conform to this type, and it is also found throughout the vast 
group of the Lejeuneae. In most of the genera of this group the branching 
is entirely of the Radida type. In a few genera of the Lejeuneae Holo- 
stipae, however, such as Stictolejeunea and Bryopteris , branching of the 
Fndlania type also occurs. These genera, together with the related genus 
Jubula (in which likewise both types of branching are found), have already 
been discussed by the writer in other connexions (’07, ’08). Whether the 
Radida type of branching occurs in other members of the Jungermanniaceae 
is doubtful, although Leitgeb assigns it to Scapania (’75, p. 29), Goebel to 
Anomoclada (’06, p. 130), and Muller to Lophozia injlata , L . acutiloba , and 
Cldloscyphus (’06-T1). The terminal branching in Lophozia and Chilo - 
scyphus , as interpreted by the writer, has been described under the Fndlania 
type, and the branching in Scapania and Anomoclada will be considered in 
connexion with intercalary branching. 
The development of the branches in Radula and the Lejeuneae is 
treated by Leitgeb at considerable length, but his statements with regard 
to the sequence of the segments in the branch-rudiments are not altogether 
consistent. This is probably due to the fact that the sequence conforms 
less rigidly to rule than in the other types of terminal branching, a condition 
clearly brought out by a comparison of fully developed shoots. In describing 
Radida (’71 <2, p. 37) he states that the first segment of the branch is basi- 
scopic (with respect to the main axis), the second acroscopic, and the third 
ventral. This would bring the first branch-leaf on the side of the branch 
turned away from the apex of the main axis, in marked contrast to what is 
found in the Fndlania type. It would also make the spirals of the branches 
on the left-hand side of the axis dextrorse and those on the right-hand side 
sinistrorse. In describing the Lejeuneae, however, he states that the first 
branch-leaf is an underleaf (’75, p. 28). This would imply that the first 
segment of the branch instead of the third was ventral in position. Even 
under these circumstances, if the first lateral leaf retains its basiscopic 
situation, the branches on the left-hand side would still be dextrorse and 
those on the right-hand side sinistrorse. The examination of a branch in 
