F. Cavers. 
230 
the plant-body is simpler in these genera than in the other Anacro- 
gynae, may perhaps be accounted for by the fact that Pellia and 
probably the majority of the species of Aneura are more hygro- 
philous than any of the other Anacrogynae; the three species of 
Pellia, and the terrestrial species of Aneura (the winged species are 
mostly epiphytic), grow in very wet places, and are often submerged 
in part. The peculiar gemmae of Aneura strongly recall the 
zoospores of the green Algae ; “ the absence of cilia from these cells, 
which probably are the last reminiscences of the ciliated gonidia of 
the aquatic ancestral forms, is to be accounted for by the terrestrial 
habit of Aneura ” (Campbell). In dealing with the genus Monoclea, 
it was suggested that the formation of a long seta, in which this 
genus differs from its allies among the Marchantiales, might be 
correlated with the extremely hygrophilous habitat. The same 
explanation may be applied to the presence of the highly developed 
elaterophore of Aneura and Pellia\ in very moist habitats the 
possession of an efficient method of spore dispersal would probably 
be advantageous, and it may be noted that the seta is longer in 
Pellia than in any other Hepaticae, while in Aneura the capsule- 
valves spring back suddenly and the spores are violently thrown out. 
In both of these lines we get numerous parallel developments, 
especially in the vegetative structure of the plant-body and in the 
investment of the sporogonium. In Aneura, the sexual branches 
are simply ordinary branches which usually stop growing in length 
after producing the sexual organs, but frequently (especially in the 
case of male branches) they resume ordinary vegetative growth 
afterwards. It may be assumed that the ancestors of the Aneura 
line produced the sexual organs on the upper side of ordinary 
thallus-branches, and that the arrest of growth which normally 
occurs in Aneura when a branch has produced sexual organs is a 
later modification. The genus which, though showing sporogonial 
features peculiar to itself, comes nearest to realising such a type is 
Makinoa, which has a well developed elaterophore and an antheridial 
receptacle similar to that of Aneura, but developed on the ordinary 
thallus. Morckia apparently belongs to the Pellia and Makinoa 
branch of the Pellia line, though its many-layered capsule-wall is 
peculiar. Morckia stands higher than Makinoa, the Aneura- like 
massive calyptra of the latter being replaced functionally by a 
perianth, outside of which a scaly cupule (involucre) is developed ; 
in Makinoa the involucre consists of a single scale. From a 
Makinoa- like form, the Symphyogyna branch of the Aneura line may 
