ol. 39 
BULLETIN ae 
TORREY BOTANICAL CLUB 
HEPATICAE OF PUERTO RICO 
XI. DIPLASIOLEJEUNEA 
ALEXANDER W. EvANs 
‘ (WITH PLATES 16 AND 17) 
In the tenth paper of this series* three genera of the Lejeuneae 
are discussed in which underleaves are entirely absent. In the 
genus Diplasiolejeunea the underleaves are duplicated; in other 
words an underleaf is developed for every lateral leaf, instead of 
for every pair of lateral leaves (PLATE 16, FIGURES land 10). The 
only other genus in which this peculiar condition is found is 
Colura, which contains some of the most remarkable species of the 
Lejeuneae, To explain the doubling of the underleaves in Colura, 
Goebel} advanced the theory that the leaves are not arranged in a 
, three-ranked spiral, as is usual in the leafy Hepaticae, but that 
# Postical segment is cut off from the apical cell after each lateral 
Segment. This being the case the leaves would be arranged in 
@ zigzag, and the imaginary line connecting their successive bases 
an not cross the antical surface of the stem at all. The 
_ €Xamination of growing points in Diplasiolejeunea brought out 
the fact that Goebel’s explanation would apply to this genus as 
: well 48 to Colura. It should be noted, however, that the duplica- 
. ton of the underleaves is not an absolutely constant feature. The 
Spee of a branch, for example (FIGURE 10), shows the ordinary 
: ‘sag arrangement, and the same thing is true of an antheridial 
throughout its entire length (PLATE 17, FIGURE 2). In the 
2 pe beets for April (39 : 139-208, pl. 10-15) was issued 17 My 1912.] 
- Torrey Club 38: 251-286. pl. rz, 12. IQII 
‘ Sanographie der Pflanzen 286 (footnote). 1898. 
209 
