2i8 Report S.A.A. Advancement of Science. 



South-Western districts, known to thie botanical geographer as the 

 Cape-Flora. 



In the extreme South "and South-West, where the winter rains 

 are constant and reguhir, the valleys and plains are covered with 

 proteas, heaths and Restionaceae, but North of the Langebergen these 

 plants do not occur :n the lower regions, being confined entirely to 

 the mountains. The reason is a twofold one, for this remarkable 

 distribution of the plants is partly due to the nature of the rocks ; 

 the mountains consisting of sandstone and the plains and hills mostly 

 of shales ; but principally it is caused by the clouds which supply 

 moisture to the plants of the mountains, but not to the valleys or 

 the hills. 



On the Zwartebergen, the Anysberg, Touwsberg, the Kamanassi 

 mountains, the Wittebergen near Matjesfontein, and a number of 

 others, the line of demarcation between the karroid vegetation of the 

 hills and the Cape-Flora is always well defined, for there is no mixing, 

 of the two formations. But even on the Cape Peninsula the contrast 

 between the region of the clouds and the lower slopes is most remark- 

 able. Many of the most famous flowers of the Cape are confined tO' 

 the mountains, where the summer climate is so largely modified by 

 the moisture-bearing clouds. The Disa uniflora, more justly called 

 D. grandi -flora, for specimens with 2 or 3 blooms are not uncommon, 

 the blue Disa graminifolia, also known as Herschelia coelestis, the 

 beautiful Disa lo7igicornu and D. ferruginea, and many other orchids, 

 do not descend below the region of the clouds. The gorgeous Nerine 

 sarniensis, the Anemone cafensis, Watsonia Meriana, and many beau- 

 tiful heaths are confined to the heights, and the Cape cedar of the 

 cedar mountains thrives at its best only above the 3000 feet level, 

 where the winter brings more rain and the summer the clouds. There 

 are hundreds, probably thousands, of species of plants which are 

 dependent on this source of supply, and cannot exist where it fails, 

 but it wouW be impossible to deal with them here. 



How considerable the quantity of water is, which the South-East 

 clouds bring, and which, it must be remembered, is not indicated by 

 our rain gauges, was well demonstrated during a five-days' South- 

 East storm in February, 1905, when the top of Table Mountain was- 

 transformed into a swamp, as if it were midwinter, although not a 

 quarter of an inch of rain had fallen during a period of three weeks. 



The area over which the South-East clouds extend is very con- 

 siderable, for it reaches from Cape Point to the Bokkeveld and the- 

 Kamiesbergen in the North, and to the mountains of Uitenhage in the 

 East, occasionally even to others further East and North. But the 

 plants referred to above as some of the chief elements of the Cape- 

 Flora, cannot thrive where the winter is dry, hence, being dependent 

 on the rain of the winter months, and an intermittent supply of 

 moisture in summer, thev are hemmed in from East and North, and 

 form a floral reg:ion of their own in a territory so small that it has nO' 

 parallel in other parts of the world. 



