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On the great sandy plains from South. West Africa and 

 Naniaqualand through Calvinia, Gordonia, and Prieska the 

 Toa grass A. brevifolia a very xerophytic, suffrutescent species, 

 covers great areas. Other important semi-desert species of 

 the West are A. ciliata, A. obtusa, A. namaquensis, A. sabuli- 

 cola, A. uniplumis, A. dregeana, A. hochstetteriana, A. suba- 

 caulis. The only characteristic species in the Cape region is 

 A. capensis. In the Karroo, and in the transitional belt 

 between Karroo and Eastern Grassveld Aristida remains the 

 most important genus, the chief species being A. congesta 

 (Steek gras), A. vestita, A. barbicollis, A. adscensionis, A. 

 bipartite,, A. stipoides var. ineridionalis, A. ciliata, A. 

 proximo, A. obtusa, A. uniplumis. 



In Eastern grassland Aristida consocies are widespread 

 in the initial stages of the prisere, the chief species being 

 A. junciformis, A. angustata, A. congesta, A. barbicollis, 

 A. bipartita, A. aequiglumis, A. sericans, A. spectabilis. 

 Through the influence of grass-burning, and over-stocking, 

 Aristida consocies become semi-stable, and often replace 

 climax Anthistiria or Andropogon consociations, forming 

 what W. G. Smith has called "substituted types." They 

 really represent initial or primitive stages of the succession. 



The species of Aristida are all xerophytic, the semi-desert 



types extremly so. They have strong, deep roots, and hard, 



wiry culms. The name "wire grass" is applied to several of 



them {e.g., A. junciformis and A. barbicollis) in the same 



way as the native name "umgongoni." Their leaves are 



narrow, usually convolute, and very hard. Their fruits 



("seeds") are capable of hygroscopic movements. If they are 



placed on the surface of moist soil they will soon be found 



to have buried themselves. Some of the seeds, e.g., those of 



A. congesta (Steek grass) bore their way even through the 



skin of sheep. All this is of importance as showing how they 



are fitted to act as pioneers, and colonize bare areas. The 



species usually grow in dense caespitose tufts which give 



shelter, and a certain amount of shade for the seedlings of less 



resistant species like Anthistiria, which usually comes up 



through the midst of the clumps. The anatomy of the leaf 



of A. bipartita is shown in Eig 6. The ridges in this case are 



prominent, with motor cells between them. The leaf folds 



in dry weather, and there are hairs on the upper surface. The 



bundles are not girdered, but there is a thick continuous band 



of sclerenchvma along the lower side, and across each of the 

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