104 
F. E. Weiss and R. H. Yapp. 
part, either Rhus viminalis or Acacia horrida, the latter often 
forming impenetrable clumps of “thorn-bush” (Fig. 3, PI. VI.). The 
only other shrub which appeared to rise conspicuously above the 
general level of the surrounding vegetation was Euclea undulata, 
which we found occasionally on rising ground. 
Near the village, in the water-courses themselves, occurred 
extensive growths of the introduced Gowphocarpus fntticosns, with 
willow-like leaves. 
Probably the great majority of the plants mentioned hitherto, 
depend largely on subterranean sources, so far as their water 
supply is concerned. 1 But in between the more conspicuous shrubs 
many smaller plants occur, which are more directly dependent 
upon the surface water available after showers of rain. The latter 
include (i.) many of the smaller succulents; (ii.) plants with under¬ 
ground storage-organs, the aerial parts of which disappear during 
the dry season ; and (iii.) annuals, the vegetative period of which 
is extremely short, the dry season being passed in the form of seeds. 
(i.) Succulent plants form a far more important feature of the 
Karroo vegetation, than of that of the deserts of North Africa. In 
fact, they comprise in some districts of the former more than 33% of 
the total phanerogamic vegetation. 2 In addition to the shrubby 
succulents mentioned above, herbaceous forms, often only a few 
inches in height, abound; e.g., different species of Crassula, small 
Mesemhrianthema, Composite with fleshy stems or leaves (Text- 
Fig. 4). 
(ii.) The aerial parts of plants with fleshy roots, tubers, bulbs 
and other subterranean storage organs spring up abundantly after 
the rains. Such are some Composite, various species of Oxalis, 
and numbers of Monocotyledons ( Dulbine , Bahiana, Moraca, etc.) 
The latter plants appeared to occur more especially on the 
comparatively low ground, rather than on the kopjes. 
In many places shallow channels, half an inch to an inch in 
depth, and perhaps a foot or so broad, had been excavated in the 
bare sandy soil, evidently by the rush of water during heavy rains. 
We noticed in many instances that these little channels (quite dry 
during our visit) contained numbers of Moraeas, while few or none 
were to be found on the surrounding soil, though the level of the 
latter was only very slightly above that of the channels themselves. 
In other cases the Moraeas occurred in more extensive patches in 
1 Schimper, loc. cit., pp. 612, ct seq. 
2 A. Engler, Ueber die Friihlingsflora des Tafelberges bei Kapstadt. 
Notizblatt d. Konigl. bot. Gart. u. Museums zu Berlin. 
Appendix XI., April, 1903, p. 42. 
