African Wildlife & Environment Issue 83

FAUNA, FLORA & WILDLIFE

V. tortilis is the only South Africa species that uniquely has these three different configurations of spines all on the same twig (truly earning the name ‘wag-‘n-bietjie haak-‘n-steek’!). It also has pods that resemble cork-screws. Harking back to my own journey with acacias, I am reminded that in 1976 Denzil Carr, who was very active in the old Tree Society of South Africa (that morphed into

Photographs above are of Faidherbia albida (Winter Thorn), that was once Acacia albida , but because of the spicate inflorescences and straight, paired, spines it was considered better to place it in a separate genus (I believe recent DNA studies support this view that was originally based on morphological features). The three photographs below are of Senegalia nigrescens , once Acacia nigrescens (Knob Thorn). Senegalia spp. are characterised by having spicate inflorescences and generally hooked prickles (these can be scattered and even paired at the leaf-base. BUT critically they are without any vascular links to the stem/xylem).

The Dendrological Society), published a 323 page ‘popular’ book on The Southern African Acacias Conservation Press (Pty) Ltd. - with a drawing of the N.W. Cape form of Acacia karroo from Aalwynkop on the title page (all but one of the beautiful pencil-sketches of the 43 species were also penned by the author). Dr James (Jim) Henderson Ross wrote the Foreword, the one and same Ross who published, in 1979, A Conspectus of African Acacia Species (Mem. Bot. Surv. S. Afr. 44 ); that was, at the time, the last word on African Acacia taxonomy. Remarkably both these acacia experts described ‘primary’ and ‘secondary’ leaves,

and Ross mentioned shoots of ‘limited’ and ‘unlimited’ growth, but neither noted the difference in the morphology of the two different leaves on said shoots! In fact, if one searches all of the available literature on acacias, no one has described the two forms of leaf separately – all leaves are simply ‘lumped’ into one! Taking this point further, I have, in my recent study of all the bushveld trees in the Kruger Park ‘discovered’ that many bushveld trees have both

The photographs at the top of the next page are all of Vachellia tortilis , once Acacia tortilis (Umbrella Thorn). Left is a small tree in full flower, and bottom right a close-up of flowering twigs. Vachellia spp. are characterised by having capitate inflorescences and straight, hooked, and one straight and one hooked, paired spines that are modified stipules .

PRIMARY and SECONDARY leaves that no one to my knowledge has previously discussed (not even the taxonomists who have recently revised many of the genera). I find this observation puzzling and so tantalizing that I am trying to investigate and collect more information on what seems to me a bushveld phenomenon - that until now has not been mentioned botanically!

25 | African Wildlife & Environment | Issue 83 (2023)