F. Cavers. 
198 
The Anacrogynae may be divided into four families, whose 
inter-relationships will be discussed later. This division differs 
somewhat from that adopted by Schiffner (54); the genus Monoclca 
has, in this series of articles, been transferred to the Marchantiales, 
while two genera discovered recently ( Makinoa and Cavicularia) are 
here dealt with, and some minor changes in classification are sug¬ 
gested, such as the splitting up of Pallavicinia into two genera 
(Blyttia and Morckia) and the restoration of the old division of 
Hymenophytum into two genera ( Podomitrium and Umbracid uni). 
AnEURACE/E. 
This family (Schiffner’s Metzgerioideae) contains four genera— 
Aneura with over 150 species, Metzgeria with about 70, Podomitrium 
and Umbraculum (united by many writers into a single genus, 
Hymeuophyton) with 2 species each. One of the most characteristic 
features common to these four genera is the restriction of the 
antheridia and archegonia to short special branches, which arise 
from the margin of the thallus in Aneura, but are ventral in origin 
in the other genera. 
The genus Aneura received its name from the fact that in the 
European species the thallus differs from that of Metzgeria in not 
being sharply differentiated into a cylindrical mid rib and a thin 
single-layered wing on either side of it, but in reality more than half 
the species of Aneura now known do show this differentiation, which 
is present in all the species of the other three genera. In several 
of these winged and often epiphytic species of Aneura there is 
considerable differentiation of the thallus branches. 1 In A. bogo- 
teusis the branches arising on one side of the creeping axis remain 
short and cylindrical and become attached to the substratum, while 
those on the other side of the axis branch repeatedly and give rise 
to broad flattened assimilating organs. In A. eriocaula and A. 
fucoides the lower branches serve as organs of attachment and, like 
the main axis itself, remain cylindrical, while the upper branches 
are erect, spreading, flattened and differentiated into mid-rib and 
wings. In other species there are various adaptations for the 
retention of water by capillarity. In A. hymenophylloides the 
branches have strongly incurved margins, forming water-sacs. In 
A. fuegiensis the same purpose is served by longitudinal lamellae 
which project from the lower surface of the thallus. The genus is 
of great interest as showing the possibilities of the simple thallus, 
1 Several of these species are figured by Goebel (17). 
