358 



BOTANY OF THE LIVING PLANT 



of the lamellae are actually the outer surface of the leaf thrown into dee]) 

 folds, and the leaf itself is part of the gametophyte, not ul the sporophyte. 



An example in the Moss-Plant of extreme simplicity is seen in Buxbaumui, 

 which habitually grows on hiimus soil, or rotting tree-stems. Its male plant 

 consists of only a single hollowed leaf, surrounding an antheridium.. The 

 female consists of a few leaves, and neither are green. Tliere is an extensive 

 green protonema, but the ihizoids show a hypha-likc habit, and establish 

 very close relations with the humous substratum. The sporcgonium itself is 



l-IG. 30n, 

 Half of a trans\'rr^c section of a leaf of Polytnclmm cuinitrjiie., ^flowing tile longi- 

 tudinal ptatLS cut in section. 



relatively large in Btixbaumia. The evidence of saprophylism is strong, and 

 it seems probable that many Mosses share that mode of irregular nutrition 

 in varying degree. 



Among the many special adaptations seen in the gametophyte of Mosses 

 one of the most peculiar is that of the T3og-Mosses (Spliagniim) : it is shared 

 in some degree by the quite distinct genus. Leucobryiim. The tissues of stem 

 and leaf include not only living cells with active jirotoplasts, but also dead 

 cells of larger size, with their walls propped out by annular or spiral fibrous 

 thickenings, and opening by round pores to the outside. They form a capillar\- 

 system by which water is retained as in a sponge. It is this structure which 

 gives Sphagnum its value for surgical dressings. These Mosses occupy large areas 

 under cold wet climates, and their dead bodies a?e the chief constituent of peal. 



The permanent establishment of new Moss-Colonies is largely due 

 to the profusion of their methods of vegetative propagation. Pro- 

 ioiieina is a regular preliminary to the formation of Moss-Plants. A 

 filament may arise from any undamaged cell, either of the plant itself 

 or of the protonema. If a sod on which Mosses are growing is 

 inverted and kept moist, protonema and ultimately a new crop of 

 Moss-Plants will arise from the rhizoids already there. If leaves or 

 stems be choppcfl up, any undamaged cell may grow ovit under favour- 

 able circumstances into protonema, giving rise to a new crop. But 



