220 PROCEEDINGS OF THE 



find it." So much does Dr. Livingstone seem to have been struck 

 with this peculiar tuber-bearing character of the vegetation, that he 

 suggests elsewhere to the Cape. farmers the possibility of growing 

 grapes in the more arid parts of Cape Colony by means of the 

 Angola tuber- bearing variety of vine. Another African traveller, 

 who devoted much attention to the botany of the regions through 

 which he passed, has carefully recorded similar features observed 

 by him in the vegetation of Central Africa, in the district around 

 the river Gazelle (a tributary of the Nile). Dr. Schweinfurth, in 

 his work on the " Heart of Africa," describes this land of Bongo, 

 which lies between latitudes 6° and 8° N., where the soil is allu- 

 vial, as being decidedly less varied than even the most uniform dis- 

 tricts of Germany, although subject to periodic rainy seasons. A 

 characteristic feature of the region is its steppes, which are subject 

 to annual conflagrations. There are, too, as he mentions, pasture 

 lands, interrupted here and there with impenetrable thickets, while 

 in the shade of certain trees are found the splendid bulbs of the 

 Eaemanthus gloriosa and Chlorophytum, together with ground 

 orchids and the wonderful " Kosaria," which is a tuber-bearing 

 plant. Upon the drier spots, where the clay soil happens to be 

 mixed with sand, weeds and herbaceous plants are found, which 

 recall the flora of the northern steppes. Many species of Cappari- 

 daceae, e.g., Gynandroj^sis, were abundant — an order which, while 

 resembling our own Cruciferae in the arrangement of its floral 

 envelopes and pungent juices, appears to bear the same relation to 

 other tropical vegetation that many of our common Cruciferae with 

 with acrid juices bear to the flora of our temperate clime. Dr. 

 Schweinfurth mentions also two leguminous plants cultivated at 

 Bongo, which fructify below the soil — the speckled pea-shaped 

 Voandzeia and the Arachis, or earth-nut, now dispersed every- 

 where over the tropics, but whose proper home is in Africa. 

 Plants having similar hypocarpogeal fruits are alluded to in the 

 course of Livingstone's writings. Of the tuberous vegetables 

 cultivated by African tribes, there are various kinds of yams 

 ( Dioscorea alata and Helmia bulbifera), by some tribes, whilst 

 the Niain-Niain and Monbutto, who devote more attention to the 

 growth of tubers than of cereals, prefer the sweet potato (Batatas 

 edulis), the " Manioc" (Euphorbiaceae),the "Colocasia" (Aroideae), 

 and other bulbs. All the yams in these parts are seen to exhibit 

 the same form, which is reckoned the most perfect in this produc- 



