Xerophytic Adaptations of Bryophytes. 185 
(e) A Persistent Protonema enlarges the area from which 
moisture may be obtained, and as it also increases the bulk of the 
plant must also assist in the conservation of moisture. When, 
owing to drought, the protonemal filaments become dried up, the 
evaporation from the surface of the soil is retarded by its covering 
of dried-up filaments. The thalloid protonemata of Sphagnum, 
Tetraphis, CEdipodium, Andrecea, Schistostega and Diphyscium may 
also act in a capillary manner, but their biological significance is in 
their assimilatory functions, whilst the discoid protonemata of some 
Andreaeae and many liverworts act as water-storers. 
(9). Vegetative Methods of Reproduction. 
These bear some relation to xerophily, as is evident on studying 
the distribution of brood-bodies, these being found chiefly amongst 
the plants which prefer dry habitats. During sexual reproduction 
and the growth of the zygote, greater quantities of food and moisture 
are required than in the ordinary life of the gametophyte, and the 
partial elimination of the sporophyte, being concomitant with a 
reduction in the amount of water required, must have some influence 
on the habitat of the bryophyte. Gemmae are produced in a very 
large number of species of both mosses and liverworts ; filiform 
ramuli in Plagiothecium elegans, Leucodon sciuroides, Fissidens 
Curnowii, Dicranumfiagellare, some species of Neckera and Grimmia, 
many species of Bryum, Amblystegium compactum, Lejeunea cavifolia 
and some species of Bazzania, Aplozia, Eucalyx, Hygrobiella, 
Eremonotus, Radula, Herberta, Adelanthus, etc. In some plants 
proliferating runners or stolons are formed as in some species of 
Thuidium, Hylocomiurn, Mnium, Eurynchiutn, Brachy the cium, Plagio¬ 
thecium and Hyrcomium, in others detached portions form a ball 
and may be carried some distance by the wind, e.g., Weisia tortilis, 
Porotrichum alopecurum, Trichostomum tortuosum. Deciduous leaves 
and shoots are formed in Campylopus, the protonema is often more 
or less persistent and almost any part of the plant is able to 
propagate the species. The fallen leaves of Campylopus, Trichostomum 
nitidum, Barbula sinuosa, etc., no doubt chiefly aid in retarding 
evaporation by covering the living plant with dead material. 
Dormant buds may also be mentioned here. Drying may take 
place to such an extent that the outer leaves perish, only the inner 
leaf-buds protected by the encircling and perishing leaves remain 
alive and resume activity on the return of moister conditions. In 
some plants of mobile soil (e.g., Tortula ruraliformis and Tricho¬ 
stomum flavovirens of sand-dunes), most of the plant is buried in 
the soil, the apices being thus preserved from desiccation. 
