Xerophytic Adaptations of Bryophytes. 163 
in water have this character absent or less pronounced, it may be 
considered a xerophytic device, especially as A. crenulota is the 
Aplozia most frequently found in dry situations, and has few other 
protective characters. The incurved margin of the leaf in Odonto- 
schisuin Spliagni is of a different nature, though it serves the same 
purpose. It usually consists of two layers of cells which are 
smaller and more incrassate than the central ones. This liverwort 
grows on Sphagnum , but the bog-moss is often more or less decayed, 
and the habitat may be a fairly dry one. Riccia sorocarpa also has 
thick-walled epidermal cells. 
(3) The Shape of the Leaf or Thallus. 
(a) Involute Leaves. The upper portion of the leaf is incurved, 
the margins being rolled inwards to form a kind of tube, so that 
evaporation is reduced. IVeisia crispa, W. crispata, W. viridnla 
(Fig. 3, 10, 11), W. tortilis, Dicranodontium longirostre, Dicranum 
scoparium v. spadiceum, Tor tula papillosum show this character. 
( b ) Cucullate Leaves. The apex of the leaf is inbent to form a 
hood enclosing a cavity, the assimilating area remaining the same 
whilst evaporation is reduced, e.g., Tortula brevirostris, T. ambigua 
(Fig. 3, 15), T. aloides, Polytrichum sexangulare, Tricliostomuni 
crispulum, T. inclinatum, T. flavovirens, Encalypta streptocarpa, 
Grimmia unicolor, IVebera cucullata, Cylindrothecium concinnum. 
The inturned apices of the leaf-lobes of Lophozia atlantica 
(Fig. 2, 3), Gymnomitriwn alpinum, Colurolejeunea calyptrifolia, 
Cephalozia bicuspidata v. conferta, Alicularia Breidleri, Lepidozia 
reptans (Fig. 2, 1), Anastrophyllum Donianum, Gymnocolea inllata 
f. nigricans (Fig. 2, 7) and some other liverworts answer the same 
purpose. 
(c) Revolute leaves. The margin is bent backwards in Tortula 
muralis, T. ruralis (Fig. 3, 12), T. intermedia, Barbula revoluta, B. 
Hornschuchiana, B. gracilis, and some other xerophytic mosses 
(species of Grimmia, Orthotrichum and Bryum). 
(d) The Concave Leaf. The boat-like leaf not only reduces the 
evaporation whilst maintaining its photosynthetic standard, but also 
provides a chamber which holds moisture, moreover the water¬ 
holding power is increased by the close approximation of the leaves. 
The concave leaf is very common amongst the bryophytes, and may 
be especially noticed in Bryum argenteum, B. capillare v. elegans, 
Brachythecium purum, B. illecebrum, B. ccespitosum, Eurynchium 
erassinervium, E. piliferum, E. circinatum, E. tnurale v. julaceum, 
