loS THE BOOK OF NATURE STUDY 



other damp, shaded places. Beside streams we get another kind 

 of thyme thread -moss, Mnium punctatum, easily recognised 

 by its large, round or oval, dark-green leaves. The Flat Fork- 

 Moss (Fissidens) has its leaves in two rows lying in the same 

 plane (Fig. 23, A, B). The leaf of this moss is of a peculiar form ; 

 the basal part is apparently split into two blades which clasp 

 the stem. The plant grows in patches on clay banks in woods, 

 and its fruit (formed in winter) consists of a small erect pointed 

 capsule on a red stalk. The Broom Fork-Mosses (Dicranum) 

 are tall plants (two to five inches high), with the leaves mostly 

 turned in one direction ; the sixteen peristome teeth, each of 

 which is cleft about halfway into two or three parts, stand up 

 when dry and bend down when moist. The woodland kinds 

 of hair-moss will be mentioned presently. The mosses which 

 are confined to moist woods are not adapted to withstand drought, 

 but soon wither and die when pulled up and allowed to get dry. 



One of the commonest mosses in dry woods is the White- 

 Leaved Fork -Moss (Leucobryum), which grows in compact, 

 rounded cushions, sometimes a foot across, and occasionally 

 quite spherical. The cushion consists of closely packed stems 

 radiating from the base, and the plant is pale bluish-green when 

 moist, nearly white when dry. The crowded leaves are rolled 

 up at the edges, and, as we should expect, resemble those of 

 Sphagnum in having water-storing cells. This moss appears 

 withered and dead in dry weather, but revives to active growth 

 when moistened. We have here an interesting case of a prac- 

 tically identical adaptation shown by two plants which live in 

 very different habitats. But the water-storing leaves of Sphagnum 

 are thin and delicate, and Sphagnum can only grow in places 

 which are more or less permanently moist, while the leaves of 

 Leucobryum are thick and robust, so that the plant is able to 

 endure a long period of drought. Sphagnum occurs only in bogs 

 and very wet woods, Leucobryum in dry woods and also on heaths. 



The following are common on roadsides and on walls. Apple- 

 Moss (Bartramia), on sandy banks, forms yellowish-green tufts, 

 the crowded narrow spreading leaves giving the plants a star- 

 like appearance as seen from above. The young capsules in 

 spring are nearly globular and pale-green, resembling miniature 



