1953] 



VEGETATION OF NYAS ALAND 



189 



river plains and the mountains, obscured what would otherwise have been a fine 

 view of the winding river and the heights of the eastern escarpment. The intense 

 heat of the sun practically limited field work to the first few hours after day- 

 light, and late afternoon. Maximum shade temperature rose to 97° and 98° F., and 

 one evening at 8:30 the thermometer stood at 88 degrees. Average annual rain- 

 fall was about 30 inches. 



Lining the high riverbank at Chikwawa were very dry forests with brushy, 

 thorny undergrowth and an assortment of much-branched trees up to 70 or 80 

 feet tall. This forest was largely deciduous and leafless and barren of flowers 

 and fruits. Tamarindus indica L. and Pterocarpus antunesii (Taub.) Harms were 

 common trees, and a Strophanthus, probably S. kombe Oliv., occurred as a large 

 scrambling shrub. Large shrubs or small trees of the dense undergrowth included 

 Azina tetracantha Lam., Courbonia glauca (Klotz.) Gilg & Bened., Capparis rosea 

 (Klotz.) Oliv., and ? Acalypha 17896. Macrorungia formosissima (Klotz.) C. B. CI. 

 was abundant as a stiff subshrub. 



Out from the riverbank the elevated alluvial plain carried patches of the 

 closed forest and a type of tall woodland or savanna forest in which Acacia 

 albida Del. and Cordyla africana Lour., the latter with new leaves and a pro- 

 fusion of fragrant yellow flowers, were characteristic large trees of 60 to 80 

 feet. Albizzia barveyi Fourn., Loncbocarpus capassa Rolfe, Boscia salicifolia 

 Oliv., Royena macrocalyx Giirke, Steganotaenia araliacea Hochst., and other 

 species occurred as small trees. Many deciduous species of the woodlands were 

 leafing out and flowering. Fires had left only remnants of a dense grass cover. 



Dry stony ridges west of the river plain were occupied by woodlands of 

 smaller trees, 20 - 50 feet tall, mostly deciduous and more or less bare of leaves. 

 Sterculia quinqueloba(Ga.rcke) K. Schum.,made conspicuous by its smooth whitish 

 bark, Combretum transvaalense Schinz, and C. ternifolium Engl. & Diels, were 

 abundant elements. Other common trees included an "ebony" (Dalbergia me- 

 lanoxylon Guill. & Perr.) forming pure stands locally, Pterocarpus angolensis 

 DC, Diospyros kirkii Hiern with edible orange-colored fruits, Stereospermum 

 knuthianum Cham., and Diplorrhynchus condylicarpon (Muell. Arg.) Pichon. 



Toward the Mwanza tributary of the Shire, about 15 miles south of Chikwawa 

 by road, parts of the sandy river plain were occupied by an open forest or sa- 

 vanna forest type of vegetation containing baobab trees (Adansonia digitata 

 L.), Combretum imberbe Wawra, Sterculia africana (Lour.) Fiori, and S. appendic- 

 ulata K. Schum., the latter a striking tall tree with blotched sycamore-like bark. 

 Areas of brushy deciduous forest, habitat of the rare nyale. antelope, contained 

 numerous very large baobabs and a tall columnar Euphorbia. Sausage trees 

 (Kigelia) grew plentifully on low alluvial ground, and Acacia xanthophloea Benth., 

 with bright yellow bark, on floodplains. Groves of Hyphaene crinita Gaertn. were 

 a feature of the Mwanza area. These very tall fan-palms stood in hundreds in dry 

 open forest, but many of them had been topped and killed by native toddy tappers. 



The Mwanza in its lower course was a wide sandy drift, fully 100 yards 

 across, with shallow trickles of clear water braided out over the sand. Major 

 elements of rich herbaceous growths on sandy beaches included Cyperus macu- 

 latus Boeck., C. polystachyos Rottb., Fimbristylis dichotoma (L.) Vahl., Pen- 

 nisetum purpureum Schumach., Epaltes alata (Sond.) Steetz, Nidorella microce- 

 phala Steetz, tall Sesbania sesban (L.) Merr., and trailing Merremia tridentata 

 (L.) Hall. f. and Ipomoea aquatica Forsk. Nymphaea lotus L. produced its white 

 flowers in muddy pools in side channels. 



In five field days, October 2 to 6, 139 botanical numbers were collected in the 

 Chikwawa and lower Mwanza areas. 



