292 
F. Cavers. 
the old genus Lejeunea, now broken up into about 
sixty genera. Frullania , the sub-genera of which 
should perhaps be treated as independent genera, is 
sharply distinguished from the Lejeuneas by its helmet¬ 
shaped water-sacs, though the genus jfubula, as shown 
by Evans (16), forms in various respects a connecting 
link between the Lejeuneas and the Frullanias. The 
most remarkable of the Lejeuneas is Metzgeriopsis 
(Thallolejeunea ). 
B. Leaves various as to form and insertion ; perianth rarely 
with longitudinal wings; capsule usually long-stalked; elaters 
numerous and arranged in various ways but never fixed above or 
extending from roof to floor of capsule-cavity ; each elater with two 
or more spiral fibres; archegonia always more than four, usually 
numerous, in a group. 
a. Leaves typically with two lobes folded upon each other and 
differing in size and often also in form. 
2. —Porellacee:. Lower leaf-lobe small, flat or concave, 
but never saccate or bearing rhizoids; underleaves 
present; perianth dorsiventrally compressed; capsule- 
valves not extending to base of capsule. Only genus 
P orel la. 
3. —Pleuroziacee:. Upper leaf-lobe larger than lower, 
the latter saccate and often provided with a trap-door 
mechanism; underleaves absent; perianth elongated 
and folded. Only genus Pleurozia. 
4. —Radulacee. Upper leaf-lobe much larger than lower; 
rhizoids borne in tufts on the lower leaf-lobes instead 
of on the stem; underleaves absent; perianth dorsi¬ 
ventrally compressed, smooth. Only genus Radula. 
5. —Scapaniacee. Upper lobe of leaf smaller than lower; 
underleaves small or absent; perianth either cylin¬ 
drical or dorsiventrally compressed, usually folded. 
Chief genera Scapnnia, Diplophyllum, Gottschea, 
Balantiopsis. 
b. Leaves either entire, or with toothed or lobed margins, or 
deeply lobed, but with the lobes equal in size and form. 
6. —Ptilidiacee. Leaves generally with several long 
teeth or lobes; underleaves always present and 
