324 MESOPHYTES sect, xvi 



insects, as well as by its fresh-green tint ; in the former respect it contrasts 

 with the likewise green and very similar meadow-moor, which is poor in 

 flowers. Between the herbs, especially when these are short, one often 

 finds many mosses, including species of Hypnum, Aulacomnium, Mnium, 

 and Bryum. Lichens, on the contrary, are wanting. 



The resting period of the vegetation is occasioned only by frost ; and, 

 although in winter it is yellowish-grey and faded, meadow oecologically 

 approaches very near to evergreen vegetation, for under the old leaves 

 fresh green ones lurk, and many yellow leaves in a mild winter recover 

 their green colour. In mild winters meadow may be green without 

 interruption. Grass commences to grow at a temperature of ii to 12-5 C. 



ADAPTATIONS 



The vegetation shows the following adaptive characters : 



1. The vast majority of the constituent species are perennial. For 

 monocarpic plants (hemi-parasitic Rhinantheae excepted) there is neither 

 sufficient light nor sufficient space ; yet a few annuals and biennials, 

 such as Linum catharticum and Cirsium palustre, occur. 



2. Some species have creeping rhizojnes, and are thus excellently fitted 

 for producing a carpet of vegetation. Among grasses thus equipped are 

 Poa pratensis, Festuca rubra, Agrostis vulgaris, and A. alba ; among 

 sedges are several species of Carex ; among other perennial herbs are 

 Lathyrus pratensis, Valeriana dioica, Epilobium palustre, Mentha, 

 Lycopus, and Equisetum palustre. 



3. Yet the majority of the grasses present are caespitose ; such is the ,; 

 case with Aira caespitosa, Avena pubescens, Dactylis glomerata, Alope- 

 curus pratensis, Anthoxanthum, Festuca elatior, Poa trivialis, Briza 

 media, and Holcus lanatus. Indeed little or no power of vegetative 

 locomotion characterizes most of the perennial herbs, such as Myosotis 

 palustris, Rumex acetosa, Succisa pratensis, Geranium pratense, Poly- 

 gonum Bistorta, Lychnis Flos-cuculi, Parnassia, and species of Ranun- 

 culus, Caltha, TroUius, and Primula. The reason for this is probably the j 

 resistance opposed to species with travelling shoots by the numerous, 

 tough, and tangled roots and rhizomes of the grasses. Bulbous and 

 tuberous plants are more uncommon, but are represented by Orchis and 

 Colchicum autumnale. 



4. The leaves are thin, flat, broad, flexible, and glabrous ; they possess |j 

 neither thick-walled epidermis nor any other special means of protecting j 

 themselves against excessive transpiration. The leaves of the grasses || 

 show stomata on both faces and are incapable of rolling up. Mechanical ' 

 tissue is developed to little or no extent. i 



FLORA 



The flora of different meadows varies widely, in harmony with dif- 

 ferences in moisture of soil, geographical situation, and agricultural 

 practice (grazing, mowing, ditching, irrigation, and so forth). Weber,^ 

 for instance, recognizes several ' sub-formations ' of natural meadow. 

 Among these we must regard as mesophytic meadow that which occurs 



* Weber, 1892, 



I 



