THE PLANT SUCCESSION IN THE THORN VELD. 1 6/ 



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Undergrowth in the Thorn Veld. 



The herbaceous undergrowth in Thorn Veld and Thorn 

 Scrub is not luxuriant, but it includes a large number of species 

 which occur more or less sporadicall}^ Some of the more char- 

 acteristic ones have already been mentioned. The species vary 

 considerably in different parts of the country. There are a 

 number of ferns — e.g.. Chcilanthcs hirta, Doryopteris concolor, 

 Pellaa viridis with var. glauca, Aspleniiim cuneatum, A. furca- 

 tiim, Dryopteris hcrgiana. Ceterach cordatitm. Moliria caffrormn, 

 Ophioglossum vulgatum (occasional), with Adiantmn capillis- 

 vencris and Dryopieris thclypteris in wet places, Pclhca Jiastata 

 on stones, and Dryopteris athamantica in ant-bear holes. The 

 numerous bulbous plants are more characteristic of the open 

 veld, but many of the veld species occasionally occur under the 

 thorn-trees — e.g., species of Scilla, Oruithogalum, Driniia, Al- 

 buca, Urginca, Tritonia, etc. Species of Asparagus are also 

 characteristic of open veld as well as under thorn-trees, but 

 they, on the whole, ])refer the latter situation. Sanseviera 

 thyrsiflora (Hgemodoracese) is a very characteristic species 

 among the undergrowth. Among the Dicotyledons various 

 Labiatse — e.g., Ocinium spp., Orthosiphon spp., Leucas spp. — 

 are common. There are several Acanthaceae which are frequent, 

 Barleria obtiisa, species of Peristrophe, Hypa^stes, Justicia, Iso- 

 glossa, etc. Verbenacese are represented by Lantana sahi folia. 

 Lippia asperifolia, and others. Some of the parasitic Scro- 



phulariace?e, such as Melasma, Harveya, are occasionally found. 

 The various climbing Asclepiads already referred to are quite 

 a feature in places. Dregea floribunda, Sarcostemma viminalis, 

 Ceropegia spp., and Riocrenxia tornlosa are among the com- 

 monest. The stem succulent, Hnernia hystrix, also occurs, 

 though it is more characteristic of open veld, sometimes covering 

 the nests of Tenncs laterieiiis. Species of Crassula are common 

 in rocky places. Poly gala spp. are occasional. The very large 

 number of species belonging to the Orders Leguminosege and 

 Compositse so abundant in the open veld are not common under 

 the thorn trees. They prefer full sunlight. 



Seed Dispersal in the Thorn Veld. 



As already pointed out, wind plays a very unimportant part 

 in the dispersal of the Thorn Veld species. This, indeed, applies 

 generally to all forest species in South Africa. There are not 

 very many Compositse in the Thorn Veld, and even among 

 them some — e.g., Osteospermum — are not distributed by wind. 

 The species of Combrefuin have winged fruits, but they are not 

 carried very far from the parent tree. In the few cases where 

 the seeds or fruits are carried by the wind it is possible that 

 the very numerous large spiders' webs (Argiope sp.) which are 

 such a common feature of the Thoni Veld, stretching between 

 the branches of the thorn-trees or between separate trees, may 

 play an important part in catching such seeds. They would 



