6 Evans.— Branching in the Leafy Hepaticae. 
orientated than those which come later. Segment 1 ', for example, in 
Fig. 5 , is not exactly ventral, but forms a considerable angle with the lower 
surface of the shoot, and segments o! and 3 ' are also somewhat displaced. 
The differences in form are partly to be looked upon as reversions to a more 
juvenile condition, and partly as modifications associated with differences in 
environment. 
The Frullania type of branching is more widely represented among the 
Jungermanniaceae than any of the other types of terminal branching. Some 
of the genera which show it have incubous leaves, some have succubous 
leaves, and some have complicate leaves. They include members of all 
the subfamilies recognized by Schiffner (’93-95) with the exception of the 
Scapanioideae, the Stephanoideae (Raduloideae), and the Pleurozoideae. 
In certain genera, such as Frullania , Porella , and Blepharostoma , the 
branches all conform closely to this type ; in other genera the Frullania 
type of branching occurs in connexion with other kinds. In Bazzania , for 
example, branches of the Frullania type 
and intercalary branches are both present, 
while in Stictolejeunea and a few other 
genera of the Lejeuneae terminal branches 
of both the Frullania type and the Radula 
type are developed. A number of char- 
acteristic examples of the Frullania type 
of branching will now be considered 
in detail. They are selected in order 
to show the modifications associated 
with the various methods of leaf-attach- 
ment. 
Frullania. — The normal leaves throughout this genus are deeply 
complicate-bilobed, the dorsal lobe being much the larger of the two. 
The ventral lobe, or lobule, usually develops a hollow water-sac with the 
opening turned towards the base of the stem or branch. The underleaves 
are almost always bifid. The modifications usual at the base of a branch 
are clearly shown in F. Asagrayana , a common species of eastern North 
America. A fragment of a branching stem is represented in Fig. 6 with the 
base of the branch on the left-hand side, and it will be noted that both 
spirals shown are sinistrorse. The incomplete leaf developed from the 
same segment as the branch consists of the dorsal lobe only ; it spreads 
more obliquely than the other leaves, being almost symmetrically situated 
with respect to both stem and branch. The line of attachment (not shown 
in the figure) is partly on the stem and partly on the branch. The first 
underleaf of the branch is at the junction with the stem, and its line of 
attachment extends around the base of the branch until it almost meets 
the line of attachment of the incomplete leaf. Apparently, however, the 
Fig. 6. Frullania Asagrayana. Led- 
yard, Connecticut (A. W. E.). x 36. 
