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The leaf anatomy of the southern African Ficusspp. is compared and discussed. The characteristics of the epidermis and mesophyll appear to be of particular value in the delimitation of taxa at subgeneric level. A key for identification of the southern African species, based on anatomical characteristics of leaves, is provided.

The germination of Citrullus lanatusseeds is extremely sensitive to water stress. A decrease of 13,6 % in the total water content is sufficient for the complete inhibition of germination. Exposure of seeds to water stress at a very late stage of germination after normal incubation in water prevents radicle emergence. Prolonged water stress treatment does not induce secondary dormancy in these seeds. Water stress which completely inhibits germination does not appear to affect the conversion of phytochrome intermediates to Pfr or the photoreversibility of phytochrome during light treatments.

The amount of absorbed solar radiation is an important factor in the energy balance of leaves and depends largely on their spectral properties. In a Sourish Mixed Bushveld (Roodeplaat Dam Nature Reserve, Transvaal) measurements of the spectral properties of leaves of 26 trees and shrubs were made to determine whether or not the occurrence of a species under the different radiation regimes (inside a bush clump or in the open) is influenced by these spectral properties.

Ninety legume species were investigated for the presence of Rhizobium-type root nodules. Only three species, namely Xylia torreanaBrenan of the Mimosoideae and Guibourtia conjugata(Bolle) J. Leonard and Piliostigma thonningii(Schumach.) Milne-Redh. of the Caesalpinioideae appear to lack the ability to nodulate. Fifty-nine of the species investigated were not studied previously in this regard. The nodulation observed on two Lipariaspecies also represents the first nodulation reports for members of this genus.

The germination of Citrullus lanatusseed is under phytochrome control. The optical properties of the fruit of this species indicate that the quality and intensity of light which penetrates the fruit could be an important factor in the inhibition of seed germination within the fruit.

Germination of Citrullus lanatusseed is inhibited by white light. The nature of the light inhibition resembles that of a low-energy reaction. Removal of the outer seed structures, especially the membrane enveloping the embryo, overcomes the inhibitory effect of light. Gibberellic acid slightly reverses the inhibitory effect of light while kinetin and particularly ethrel strongly promote the germination of seed in white light.

The underground structure of D. cymosumconsists of a root system, as well as a complex system of lateral and adventitious stems. The stem system is mainly underground and only the apical parts of the branches appear above ground level. These erect aerial parts are 50–150mm long and usually die back to below ground level each winter.

A microbiological study of ‘bare patches’ in the Giribes plains of Kaokoland, S.W.A.-Namibia. A study was made of the density of the bacteria and fungus populations in, on the edges of, and between ‘bare patches’ in the Giribes plain, Kaokoland. The density of the microbial populations showed, with the exception of anaerobic bacteria, a close relation to the density of the higher plants of these soils. The soil samples of the bare patches had the lowest microbial population level while the edge of the patches had the highest microbial population. Sixty three species of fungi belonging to 37 genera in total were isolated from these three soil types. The nature of the fungus population closely resembles those of other dry areas. Aspergillusand Penicilliumspecies were generally the most numerous while many yeasts and dark coloured Dematiaceae also occured quite commonly.

Seed populations in the soil of the Hester Malan Nature Reserve in the Namaqualand Broken Veld. Soil samples were collected at five different localities in the Hester Malan Nature Reserve in two consecutive years. The seed content of the top 25mm of soil was higher for the more disturbed localities i.e. the valley, sandy plains and plateau, than for the hills and ridges. All the localities except the sandy plains, had the highest number of viable seeds in the top 25mm of soil and showed a sharp drop in seed density at greater depths. There was no significant difference in the number of viable seeds in the soil samples that were collected at the same sampling point in the two consecutive years. In both constant and alternating temperatures, germination increased from the high to the low temperatures or temperature combinations. The established seedlings appeared to have no stimulatory or inhibitory effect on the germination of the remaining seeds in the seed bank, but periodic mixing of the soil resulted in a large increase in the number of germinating seeds. A rain spray, equivalent to 50mm of rain increased the rate of germination within the first few days.