170 THE PLANT SUCCESSION IN THE THORN VELD. 



showed to be rich in proteids and oils. These seeds, therefore 

 may possibly be considered as myrmecochorous like those de- 

 scribed by Sernander, but, if so, the ants did not seem to show 

 any very marked preference for them. Other seeds were carried 

 away as readily. 



Experiments were also carried out with another smaller 

 species of Tetramorium. This species removes the husks from 

 the grass seeds and throws the former outside its nest in little 

 heaps. These preliminary investigations are sufficient to show 

 that ants are important agents for seed dispersal in the veld of 

 South Africa. Further experiments on the subject are in pro- 

 gress. 



The Importance oe Termites. 



According to Fuller, " in Natal and the Transvaal it is no 

 exaggeration to say that the soil is riddled from end to end 

 of the country with termite tunnellings through which an in- 

 conceivable host of insects constantly passes to and fro."* In 

 two small areas of Pietermaritzburg (784 sq. yards each) he 

 reported finding 14 and 16 nests respectively, the homes of six 

 different species, an observation based solely upon surface in- 

 dications ; while at Pretoria, while excavations for the founda- 

 tions of Government buildings were being made, it was found 

 that the soil was inhabited by eig'ht species. " To a depth of 

 four to five feet it was riddled with their galleries, and not a 

 cubic yard existed which did not contain one or more cavities 

 belonging to one species or another." The white ants form 

 nests varying in form and position according to the species. 

 They are not all mound-builders, and the juvenile nests even 

 of the species that are, are often moimdless. Apart from the 

 extremely important effects on the soil conditions, which doubt- 

 less has a good deal to do with preparing the way for tree 

 growth, and the effect also on the vegetation itself (both grasses 

 and trees) there are various biological agencies other than the 

 white ants themselves which are brought into operation. The 

 mounds of Termes nataleusis, T. latericius, T. vulgaris, and 

 especially Eutermes trinervins, are conspicuous features of the 

 landscape. The outer parts of the mounds are carefully closed 

 by cemented pellicles to exclude enemies. As long as the nest 

 is inhabited these mounds are increased in size and repaired 

 against the effect of denudation. Birds flying over the veld 

 naturally alight on such mounds. They scatter seeds which roll 

 down or are washed down over the outside of the mound and 

 find a suitable germinating ground among the fringe of grasses 

 which surround the mound, or they may germinate on the 

 mound itself. This doubtless explains why a primary clump of 

 Thorn Veld species is so often established on the site of an 

 old termites' nest. The succession here differs, therefore, some- 

 what ifrom that outlined in the first part of this paper, but it 



*Fuller. Claude. " Ob.servations on Some South African Termites," 

 Ann. Nat. Mus.,S [2], (igie^). 



