22 
Evans —Branching in the Leafy Hepaticae. 
noted that both branches are dextrorse also, that the branch on the right- 
hand side has arisen in a ventral seg- 
ment-half, and that the branch on the 
left has arisen in a dorsal segment- 
half. In other words, the branch on 
the right conforms to the Frullania 
type and that on the left to the Micro - 
lepidozia type. 
When the branching in 'Micro - 
lepidozia was first studied by the writer 
(’04, p. 187) it was observed that, 
looking at a branch- system from the 
dorsal surface, none of the branches 
on one side had incomplete leaves at 
the base while all the branches on the 
other side showed such leaves clearly. 
The conclusion was reached that the 
branches without incomplete leaves 
represented entire segments, thus leav- 
ingnothing for the formation of leaves. 
Further study, however, has brought 
out the fact that this interpretation is 
incorrect and that these branches have 
incomplete leaves at the base just as 
in the Frullania type, the only difference being that they are situated on the 
ventral surface of the shoot instead of on the dorsal. It will be seen from 
the figure that the first branch-leaf in the 
Microlepidozia type is not an underleaf, as in 
the Frullania type, but a lateral leaf on the side 
of the branch turned away from the main axis, 
that the second leaf also is a lateral leaf but 
on the other side, and that the third leaf re- 
presents the first underleaf formed. None of 
these branch-leaves show special modifications. 
Sinistrorse branching systems as well as dex- 
trorse may be observed in Microlepidozia just 
as in Bazzania . 
The accompanying diagram (Fig. 29) 
illustrates the terminal branching in Micro- 
lepidozia. The oldest segment on the right 
shows the Frullania type and agrees with 
Fig. 5 ; the segment on the left shows the establishment of the apical 
cell of a branch in the dorsal segment-half, according to the Microlepidozia 
Fig. 28. Lepidozia (. Microlepidozia ) setae ea. 
Franconia Mountains, New Hampshire (A. W. 
E.). x 100. 
Fig. 29. Diagram representing 
the establishment of a branch of the 
Microlepidozia type on the left and 
one of the Frullania type on the 
right. 
