-212 R. Marloth, Ph.D., M.A.—The [Oct. 26, 



•and such trees, which abound along the river beds of those countries, 

 :afford therefore much better shelter against the sun than any other 

 species. 



The legumes of the ana-tree are broad, twisted, and not leathery 

 as are those of the other acacias. They are farinaceous and constitute 

 a very valuable food to herbiverous animals. This is probably one 

 of the reasons for the comparatively wide distribution of the ana-tree' 

 for the hard seeds pass undigested through the animals ivhich have 

 fed on its pods. 



Having become acquainted with the principal representatives of 

 this genus, it will be of some interest for us to throw a retrospective 

 glance on the various forms we have met with. We have seen some 

 species which are only a couple of feet high and others which raise 

 their lofty heads high above any other indigenous tree. We have 

 admired the rich foliage of the ana-tree and looked almost with pity 

 at the few poor leaves of the hookthorn. We found a greater variety 

 still in the formation of the pods and spines. The pods are of all 

 shapes and sizes ; linear, moniliform, oval or half-moon shaped ; 

 straight, bent, sickle-shaped or twisted ; thin and papery, leathery, 

 woody or mealy, and from one inch to six inches long. 



Fir spines, or in some cases the prickles, are straight or recurved, 

 or both kinds are combined on the same branch ; they are short or 

 long, thin or thick, glabrous or pubescent, rigid or elastic. They 

 occur mostly in pairs, one species however having three under each 

 leaf and one species only being entirely destitute of them. 



The question arises : What are the causes of such variety of 

 forms in a comparatively small number of species ? Or since our 

 knowledge of the matter at present is not sufficient to enable us to 

 grapple with the whole of such a complicated problem, we may 

 at least ask : Can any relation be shown to exist between certain 

 peculiarities of these plants and their surroundings, especially as 

 far as climate, rainfall, soil, etc., are concerned ? 



We are accustomed to find the larger forms of nearly allied plants 

 in localities which have an ampler supply of water, but this common 

 rale does not hold good in this case, as a comparison between the 

 Karroo-thorn for instance and the camelthorn shows. The former 

 although growing on the banks of perennially flowing rivers, is much 

 inferior in its dimensions to the latter, which prefers dry plains and 

 stony hills. 



" It is surprising," says Grisebach in his book Die Vegetatio7i der 

 Erde, " that such a delicate thing as the acacia-leaf is able to exist 



