ch. xxii THE TREE-LOBELIAS 251 



of " the interesting questions of the origin and development of the 

 Hawaiian flora " (see the Editor's Introduction, p. ix.). In no group 

 of plants is this want more keenly felt than with the Lobeliaceae. 

 Yet in his time the explorations had yet to be made that could set 

 the student of plant-distribution on the road to investigate this 

 problem. 



It was true, no doubt, that types analogous to those of the 

 Hawaiian Lobeliaceae were known from the American and African 

 continents. Thus Oliver in his Flora of Tropical Africa, published 

 in 1877, gives an account of the species of Lobelia then known 

 from the mountains of this region. The genus was, however, not 

 entirely confined to mountainous districts, but it would almost 

 seem that most of the high mountains of Equatorial Africa had 

 their peculiar species, some of them being tree-like and others 

 shrubby. Two mountain species were recorded from Abyssinia, 

 one of them from an elevation of 1 1,000 to 13,000 feet and growing 

 to a height of 12 to 15 feet, the other from an altitude of about 

 8,000 feet ; another, Lobelia Deckenii, attaining a height of 4 feet, 

 was recorded from the uplands of Kilimanjaro, 12,000 to 13,000 

 feet above the sea, and yet another from the mountains of 

 Fernando Po, at an altitude of 9,000 feet. So again, in the 

 case of the American continent, Hemsley, writing in 1885 {Intr. 

 Bot. Chall. Exped., p. 32), speaks of arborescent species of the 

 American genera Centropogon, Siphocampylus, &c. ; and Baillon 

 in his Natural History of Plants (Engl. edit. viii. 350) refers to the 

 similar Tupas and Haynaldias from South America. But what 

 the student of plant-distribution looked for was not merely the 

 occurrence of " tree-lobelias " in other parts of the world, but also 

 the reproduction of these wonderful plants under the same con- 

 ditions and on the same scale as those familiar to him on the 

 Hawaiian mountains. He has accordingly had to wait for the 

 results of the more recent explorations of the mountains of Central 

 Africa in order to obtain his wish. 



On the upper flanks of Ruwenzori, Kilimanjaro, and Kenya, at 

 elevations of 9,000 to 13,000 feet and reaching to the snow-line, 

 there flourish in boggy portions of the forest arborescent Lobeliaceae 

 that attain a height of 1 5 or 20 feet. They have the habit some- 

 times of a Dracaena and sometimes of an Aloe, and do not exhibit 

 the branching trunks so characteristic of the Hawaiian genus of 

 Clermontia. They all belong, however, to the genus Lobelia, and 

 thus do not display the extensive differentiation of the endemic 

 genera of Hawaii. Nor, apparently, has there been the same 



