144 SCIENCE IN AFRICA 



human or animal, etc.; (3) Selective breeding for economic pur- 

 poses; (4) Plant pathology, which again is concerned mainly with 

 crops. Plant breeding and pathology are discussed in relation to 

 other studies of each kind of crop in Chapter XII so the present 

 chapter is devoted mainly to taxonomy and ecology. Special 

 sections are devoted to the improvement of pasture-lands, to which 

 ecology is closely relevant, and to the conservation of the unique 

 flora of the continent. Several of these subjects are dealt with in 

 later chapters, notably Chapters VII, IX, and X. 



The question arises here, as in other subjects, of the value of the 

 survey method in estimating the potentialities of land. It is certain 

 that the study of ecology, and particularly that branch of the sub- 

 ject which deals with the changes in vegetation produced by 

 human intervention, is of extreme importance, and for this reason 

 considerable space is devoted to it below. Though the addition 

 of plant ecologists to the several agricultural departments would 

 be highly desirable, it must be admitted that any large ecological 

 surveys are probably not justified at the present stage of develop- 

 ment. 



Stress must be laid again on the soil-vegetation unit, since the 

 use of this as a basis of research is one of the principles which dis- 

 tinguish the ecological from the purely botanical survey. It is not 

 intended, however, to minimize the importance of the relation 

 between plants and climate, physiography and animals, all of 

 which must be included in any ecological study. As the science 

 advances it becomes increasingly evident that one man cannot deal 

 with all aspects, and recourse must be had more and more to team 

 work. 



Studies on ecology and most researches devoted to breeding and 

 pathology can only be carried out in Africa itself As regards 

 taxonomy, the position is somewhat different because the flora of 

 Africa is so diverse that one expert can, as a rule, only deal effec- 

 tively with a comparatively small group. Moreover, owing to the 

 fact that most of the African flora has been described by botanists 

 working in European herbaria, the 'type' or authentic specimens 

 of the species described are preserved in British or Continental 

 institutions. Therefore, however carefully field studies are now 

 carried out in Africa, the taxonomist must still largely rely on 



