SECTION B. 



I S— PRESIDENTIAL ADDRESS. 

 By R. Marloth Ph.D.. M.A. 



Thk Historical Devllopment of the Geographical Botany 

 OF Southern Africa. 



Among the various branches of botanical research, which recent- 

 ly have received special attention, is hardly one which has develop- 

 ed itself more rapidly than Geographical Botany. The principal 

 reason for this rapid growth of interest in this special study is the 

 recognition, that the field is a much wider one than was generally 

 thought. It appears to me therefore desirable to indicate from the 

 outset the range of the subject as understood by modern botanists. 



The various tasks, which the geographical botany of a country 

 comprise may be arranged in three groups. The first step is the 

 study of the distribution of the plants as we find them at present. 

 For this purfKDse collections of plants have to be made in the various 

 districts and these results have to be tabulated according to orders, 

 genera and species, and to be compared with each other and those 

 of other regions. The range of species, genera, orders and classes 

 has to be ascertained, and the conclusions drawn from these observa- 

 tions concerning the relationship of the vegetation of the country 

 compared with that of other regions. 



Although this studv will reveal many interesting facts, it can- 

 not give us a true insight into the character of the vegetation. The 

 next step will be the studv of the societies of plants as we find them 

 in nature. One has to examine these natural associations, which 

 mav occur in different jiarts of the country, not only with regard to 

 the elements that form them, with regard to the various species that 

 occur in them, but specially with regard to the conditions under 

 which they exist. The influence of soil and climate, of heat and 

 cold, of rain and drought, of light and shade, of insects and other 

 animals, of human interference and of all other causes, which are 

 liable to affect the life of a plant, have to be studied. When all 

 these conditions are known, which is hardly ever the case, we shall 

 be able to understand, whv a certain plant occurs in one locality and 

 not in another. 



We shall, however, not yet know how it came there. In order 

 to gain an insight into the life-histon,- of a particular species of 

 plants, it would be necessar\- to know something aliout its ancestors. 

 In countries with younger geological formations a good deal of 

 information of this kind has been ol)tained from jjaiaeontological 



