390 SCIENCE PROGRESS. 



approximately the number of species of vascular plants 

 growing wild in the Canaries, Dr. Christ would deduct up- 

 wards of a third (420) as not being really indigenous ; in 

 other words, as not belonging to the original flora. This 

 leaves 806 species, of which 414 are endemic in the Atlantic 

 Islands ; and 392 are also continental. About the same 

 percentage obtains in the West Indies ; but it is much 

 higher in Mexico, South Africa, and East and West Aus- 

 tralia. Still the peculiarity of the Atlantic Islands flora is 

 rather in the habit of the endemic species than in their rela- 

 tive number. By habit I mean vegetative characteristics, 

 which give the endemic plants a vital energy sufficient to 

 enable them to hold their own against all intruders. On 

 this point Dr. Christ has collected a number of highly inter- 

 esting facts. Grisebach (32) was of opinion that the en- 

 demic flora of the Canaries was dying out, and would soon 

 be exterminated by the more vigorous colonists from the 

 continent. Happily, says Christ, this is an error. C. Bolle, 

 the most experienced and exact among Atlantic botanists, 

 pointed out long ago (t,^,) that the native flora would in- 

 definitely survive in spite of cultivation, and the protection 

 afforded by man to introduced plants. The apparently pro- 

 scribed plants were constantly gathering new strength to 

 recover the lost ground. "In short," Bolle says, " it (the 

 endemic flora) is everlasting, indestructible ; and vast tracts 

 of country not forfeited to cultivation are still exclusively 

 left to it." Twenty five years later Dr. Christ found every- 

 where full confirmation of this statement. In the struggle 

 for existence, he asserts, the local conditions are all in 

 favour of the native plants and against intruders ; and so 

 long as the present conditions continue, so long will the 

 present flora flourish. I have already mentioned the great 

 development of the root-system of the succulent plants 

 growing on rocks ; and I may add that it is to the great 

 vegetative capacity of the native plants generally that Dr. 

 Christ ascribes their power of resistance to foreign invasion. 

 This applies more especially to the half-woody plants, be- 

 longing to genera whose continental species are mostly 

 herbaceous. The huge clumps of rosettes of Sempervivum, 

 and the dense hemispherical tufts of Echium and Statice 



