2 94 
F. Cavers. 
of framing a natural classification is increased by the occurrence of 
many features which can only he regarded as examples of homoplasy. 
Among these parallel developments, may be mentioned the following, 
which are found in widely separated genera and families:—open 
water-pitchers ( Rudula , Polyotus, Friillania, etc.); closed pitchers 
with a trap-door or valve mechanism ( Pleurozia, Colurolejeunea ); 
paraphylls ( Gottschea, T richocolea, Stephaniella, Marsupidium ); 
coelocauly—the penetration of the stem by the sporogonium 
{Gottschea, T richocolea, Polyotus,. etc.); the formation of marsupia 
of various structural types (Tylimanthus, Balantiopsis, Acrobolbus, 
Kantia , etc.). 
The Inter-Relationships of the Acrogynae. 
In discussing the inter-relationships of the Anacrogynous 
Jungermanniales, reasons were brought forward to support the view 
that the division of the Jungermanniales into Anacrogynae and 
Acrogynae is a purely artificial one. It was also suggested that the 
Anacrogynae have arisen from a thalloid ancestor, and that the 
differentiation of stem and leaves has taken place in several 
diverging lines of affinity, starting from an undifferentiated thallus. 
On these views we must assume that the Acrogynae have arisen 
from the Anacrogynae, and of the two main series of Anacrogynae 
it would appear that the Pellia series offers the natural starting- 
point for the Acrogynae, since it is in the higher members of the 
Pellia line—in genera like Fossombronia— that we find the sharpest 
differentiation into stem and leaf. 
The Lejeuneaceae are so sharply distinguished from all the 
other Acrogynae in the structure of the capsule, that some writers 
have inclined to the view that this group has arisen independently 
and that the Acrogynae form a polyphyletic group, derived from the 
Anacrogynae along two independent lines. Spruce was so deeply 
impressed by the marked characters of the Lejeuneaceae that he 
divided the Jungermanniales into two groups—the “Jubuleae” or 
Lejeuneaceae forming one group, while his group “ Jungermannieae” 
included all the remainingforms, both Acrogynousand Anacrogynous. 
Schiffner (68) considered that the sporogonium of the Lejeuneaceae 
shows such a degree of resemblance to that of the Aneuraceae that 
he suggested the independent origin of the Lejeuneaceae from a 
Metzgeria- like form, all the remaining Acrogynae being derivable 
from a form like Fossombronia. This view is adopted by Lotsy (60), 
