410 SECTIONAL TRANSACTIONS.— K*. 



projected investigation of the forest fiora of Northern Rhodesia and N3'asaland, the 

 mangrove swamps of East Africa and the woody plants of the islands of Zanzibar 

 and Pemba. 



The tour covered a period of twenty weeks from the date of leaving England, and 

 involved considerable travelling interspersed with the collecting of specimens, during 

 the whole period from the date of arrival at Cape Town on July 19. Leading the 

 British Association party at Victoria Falls, a visit was paid to the Siburu Forest in 

 the Zambesi basin, some 70 miles west of Livingstone, to see the Rhodesian teak, 

 Baikioia plurijuga, in its natural habitat on the Kalahari-sand formation. From 

 Livingstone the ' Great North Road ' to Lusaka was followed, thence to the east to 

 Fort Jameson on the Nyasaland border over the ' Great East Road,' which had been 

 opened for traffic only the previous year and was in a bad condition as regards bridges 

 and ponts. From Fort Jameson, South and Central Nyasaland was explored by 

 traverses in different directions, taking in a number of the high mountain peaks in 

 order to investigate the remnants of rain-forest still to be found there. The Northern 

 Rhodesian tour occupied three weeks, and the whole of September was devoted to 

 travelling and collecting in Nyasaland. Owing to the limited time available and the 

 i nf requency of the sailings of the lake steamers, it was found impossible to visit tie 

 extreme north-western end of the Protectorate, for which purpose the Association 

 generously made a grant in aid. In consequence, the grant has not been claimed. 



Two weeks were spent in Zanzibar and Pemba Islands, where the principal points 

 of botanical interest were visited and valuable collections were made, thanks to the 

 admirable arrangements made by H. E. the British Resident and various 

 officials. 



On my homeward voyage more collections were made at various ports of call, 

 no less than forty numbers being found at Aden, owing to the recent rains. 



Two thousand eight hundred numbers were collected in all, of which very few have 

 been worked out as yet, but these include several undescribed species. Among the latter 

 is a new species of Pterocarpus, P. stevensonii, from the Siburu teak forest, which 

 furnishes a useful timber ; this is named after Mr. D. Stevenson, the officer in charge 

 of the Forestry Service of Northern Rhodesia, who gave the information as to its 

 economic value. The tree was not in flower at the time of our visit, but Mr. Stevenson 

 has obtained flowers and fruits. Particular attention was given to the Brachystegias 

 A^hich furnish the dominant species over a large extent of the savannah-forest country ; 

 as a result, the number of species known to occur in Nyasaland has been increased 

 from ten to twenty-four species and a new variety. 



The vegetation of Northern Rhodesia, as far as this and a previous journey have 

 enabled me to ascertain, falls within the tj-pe known as the deciduous savannah-forest, 

 though varying greatly in density of growth and usually with open canopy. Remnants 

 of fringing forest occur along the larger perennial streams. The difference in density 

 and size of the component trees appears to be correlated with the amount of available 

 moisture due to the difference in amount of precipitation and in the depth and 

 character of the soil and of the soil drainage. The whole of the 700 miles crossed in 

 Northern Rhodesia is an undulating plateau of about 4,000 feet elevation, here and 

 there intersected by large tributaries of the Zambesi, the Kafue, Lunsemfwa and 

 Luangwa. There are no very marked differences in altitude after reaching the summit 

 above the Zambesi valley ; consequently the vegetation and flora are more uniform 

 in character than in regions with a more diversified topography. 



It had been supposed that the frontier between Northern Rhodesia and Nyasaland 

 might have provided a phy to -geographical boundary. This is not the case in the 

 vicinity of Fort Jameson, and one meets the same type of vegetation when traversing 

 the West Nyasa Province of Nyasaland, with no marked differences in component 

 species. On the eastern slopes of the escarpment overlooking the Lake, however, are 

 to be found remnants of true rain-forest, and a similar type of vegetation is found also 

 on the higher peaks met with in the southern part of the Protectorate. At the lower 

 levels a more definitely tropical type of savannah-forest occurs. L'^seful information 

 has been obtained on the geographical distribution and ecology of the components 

 of the flora, which are discussed in the paper. 



Afternoon. 

 Excursion to Tortworth. 



I 



