25 
Evans . — Branching in the Leafy Hepaticae. 
Radula (Fig. 31) or in one of the Lejeuneae (Fig. 32) shows that his state- 
ments with regard to the lateral leaves are correct, the first leaf being con- 
stantly basiscopic. The spirals, however, show certain deviations. The 
determination of a spiral in Radula is beset with difficulties because the 
ventral segments bear no appendages. It is only by studying the apical 
cell and the young segments that the direction of the spiral can be positively 
demonstrated. This was done in the species figured, R. aquilegia of western 
Europe, and it was found that the branch-spirals on the left-hand side of 
a branching axis were sinistrorse instead of dextrorse as Leitgeb’s account 
demands. This would, of course, make the ventral segment in the branch- 
rudiment second instead of third in the sequence, the basiscopic segment 
still being first. The conditions just described are found in both vegetative 
branches and subfloral innovations and are apparently constant throughout 
the genus. 
Fig. 31. Radula aquilegia. Moidart, Fig. 32. Euosmolejeunea dtiriuscula. 
Scotland (S. M. Macvicar). x 27. Sanford, Florida (S. Rapp), x 40. 
In most of the Lejeuneae underleaves are present, so that the determina- 
tion of a spiral is an easy matter. It is necessary here to distinguish between 
subfloral innovations and vegetative branches because they sometimes show 
differences which are not to be found in Radula. In the species figured 
(Fig. 32), Euosmolejeunea duriuscula of tropical and subtropical America, 
the peculiarities and variations of the innovations are well shown. It will 
be seen that the innovation on the right conforms closely to Leitgeb’s 
conception, the first branch-leaf being an underleaf, the first lateral leaf 
being basiscopic, and the spiral being sinistrorse. The innovation on the 
left, however, is also sinistrorse, the first leaf being basiscopic and the 
underleaf being second in the sequence. A study of numerous innovations 
has shown that there is apparently no relation between their spirals and the 
spiral of the flowering axis, although the condition shown by the left-hand 
innovation seems to be much commoner than the other. This condition 
is of course identical with what has just been described for Radula. 
