52 



•what succulent, and though slow-growing this species of 

 Danthonia is a very nutritious grass. The same applies to 

 other Western and xerophytic species. 



Another feature of xerophytes is a tendency towards 

 increased lignification. The leaves become very hard, having 

 developed a large amount of fibre or sclerenchyma. Even 

 though they sometimes contain a fairly high percentage of 

 starch and proteids, etc., cattle dislike them, and refuse to 

 eat them, if they can get any other kinds. It is very notice- 

 able how they eat out the more mesophytic species first, from 

 mixed Veld. In the various figures of leaf sections here 

 reproduced the sclerenchyma is shown by cross hatching. A 

 glance is sufficient to show whether each grass represented is 

 likely to prove palatable to stock. The less cross-hatching 

 shown, the more useful the grass from this standpoint. 



All the ordinary grasses have their veins or vascular 

 water-conducting strands parallel. These may be seen by 

 holding the leaf up to the light. The principal veins lie 

 'underneath more or less prominent ridges which have furrows 

 between them. Some leaves have a midrib which is larger 

 than the other veins, others do not. A comparison of the 

 figures will show that the ridges are very prominent in the 

 more xerophytic grasses like Aristida, and in all the temperate 

 types like A chneria, Lasiochloa, Pentaschistis, Ehrharta, Dan- 

 thonia, Brizopyrnm, while they are much less prominent or 

 almost obsolete in the sub-tropical tribes of the Andropogoneae, 

 Paniceae, etc. (Andropogon, Anthistiria, Urelytrum, Setaria, 

 Tricholaena, Panicum, Digitaria, Sporobolus, Harpechloa, 

 Chloris). The sections also show that there are often one 

 or two smaller vascular strands in the hollows between the 

 larger ones. The arrangement of the sclerenchyma is also 

 interesting. It usually lies above and below the main veins, 

 i.e., on the ridges and opposite to them on the lower side. In 

 the mesophytic types it does not join up to the vascular 

 bundles, but in less mesophytic types it forms a girder, which 

 crosses the leaf, the vascular strand lying in the middle of the 

 girder. In still more xerophytic species (c-g-, Aristida 

 bipartita, Danthonia disticha) it forms a continuous band 

 along the lower surface. Attention should also be directed 

 to the presence or absence of hairs on one or both surfaces of 

 the leaf, to the relative thickness or thinness of the cuticle, 

 to the nature and size of the epidermal cells where these are 

 shown, to the arrangement of the green chlorophyll tissue, 

 and to the jjeneral outline of the section. 



