113 



(e) Chomophyte or Crevice Successions. Rock crevices 

 and rock ledges provide shelter and a suitable germinating 

 ground for a great assemblage of species. Soil gathers and 

 may be deep, and there are all degrees of variation in the 

 amount of moisture and shade. Wind-blown seeds are blown 

 into rock crevices, and birds, which carry seeds, find there is 

 a natural sheltering place. It is not surprising, therefore, that 

 it is possible to find nearly the whole flora of a district repre- 

 sented in such situations. The crevice succession may lead 

 up to grassland or more frequently and, at least temporarily, 

 to rocky Scrub. In the Veld succession the crevices become 

 obliterated by the accumulation of soil. Definite grassland 

 demands a certain smoothness of surface, and on steeper hill- 

 sides or broken ground of any sort there remain numerous 

 clans or societies of various different species which careful 

 examination will show belong to a Chomophyte stage in the 

 plant succession. There are, of course, other species which 

 mix more intimately with the grasses and usually form distinct 

 aspect societies. 



Initial Grassland Stages. Pioneer Grasses. 



There are numerous ruderal grasses, some of them useful 

 for grazing, which form the initial grassland stages in various 

 sub-seres, which will be dealt with later. Ruderal or annual 

 species do not play any important part in the prisere, though 

 they are often present. The chief pioneer grasses are all 

 xerophytic, deep rooted, light demanding species. It is inter- 

 esting to notice that the seeds of many of them (e.g., Aristida 

 spp) are capable of boring their way down through quite hard 

 soil. Their seedlings require little or no shade or shelter in 

 the earlier stages. They grow in spreading caespitose tufts, 

 and do not form a close covering over the soil surface. Their 

 renewal buds are usually extravaginal, and buried in the soil, 

 some of them being slightly stoloniferous. They are not much 

 injured by fire. 



In a few cases (Cynodon) they are creeping forms, which 

 root at the nodes, but this type is exceptional. Owing to 

 their xerophytic nature, and the amount of hard sclerenchyma 

 in their leaves, they are not liked by cattle, and many of 

 them, especially the Aristidas, are only eaten in Spring, when 

 the young and softer leaves are produced. Nevertheless, some 

 of them, especially the species of Eragrostis, are fairly nutri- 

 tious grasses.- Cynodon is considered quite a good grass, and 

 stock are fond of it. It is interesting to notice the close simi- 



