S.A. URYOPHYTA. 4OI 



surface to the atmosphere instead of a dry rock. Rhacopilum 

 does so ill the Eastern Transvaal streams, and many t)ther species 

 are more or less constantly associated with water. 



4. Efii'inTJC Associations. — These occur either on bark 

 or on stones, or on both ; sometimes even on tree leaves or upon 

 other mosses imder forest or swamp conditions. The pioneer 

 species usually start on the slime of Alg-^e or lichens, but often 

 arrive at a condition of permanent occupation which lasts as 

 long as the suitable condition lasts, and then when the forest is 

 opened out and forest regrowth begins, these species again 

 resume pioneer service on the regrowth- 



But in addition to llie naturally pioneer species (some of 

 which have already lieen mentioned), many other succession 

 species appear after a time, sometimes as true epi])hytes, more 

 frequently as mesophytes living on the hunuis formed by the 

 decay cif earlier generations. Some are even so inde])endent of' 

 attachment that they continue to live and flourish if detached 

 from their anchorage, and hang upon branches m moist forest; 

 some, again, are so nearly parasitic that it is only upon living 

 wood that they continue to grow, while others li\e easily as 

 epiphytes either on living or dead wood, or on stones, or humus, 

 -■ometimes e.Ktending even on to soil. 



During the whole of the permanent occupation by these 

 Bryophyta the}' are of immense advantage in the economy of 

 nature in the direction of forming humus and of acting as a 

 surface sponge into which available moisture is accepted and 

 retained until wanted by changed hygrometric conditions, and 

 even in those which hang loosely, and consequently form no 

 sponge, the abihty to absorb and retain moisture inider imbri- 

 cated leaves or in other similar situations has much to do with 

 the i)ermanentlv cool and moist condition usually prevalent 

 inside a forest. It must not be lost sight oi, however, that 

 these epiphytes have often to undergo periods of intense drought, 

 and that the_\' must possess water-retaining arrangements capable 

 of collectine and enduring moistttre to an unusual degree. 



Examples of the types mentioned include : — 



A. Usuall\' pioneers ; afterwards climax type : — 



1. Leaf parasites (i.e., living on living leaves) : — Micro- 



lejeiiiiea. Radn!a. Pntllauia. 



2. Bark parasites (i.e., li\ing on living bark, and often as 



isolated plants or patches on bark ifully exposed to 

 sunshine, and frequently hi^h up the trees, or on 

 trees awav altogether from forest conditions. 



Fabroiiia, Orthotriehnm, Fritllania, 



Maeroiiiitniiin sps. Radula, etc. 



3. Ei'ii'UM'Ks ox Living Bryophyta: — 



Ell- lej'e u nea, F in i b ria r ia , 



Mct::geria, Kantia, 



Radula. Ceplialocia, 



Fnillaiiia Rcklonii, Lepido.da, etc. 



