760 POPULAR SCIENCE MONTHLY. 



remote date is clearly evidenced by the great development of 

 peculiar species of continental genera. Moreover, Saporta proves 

 that types now foimd only in the Canaries (or perhaps also in Ma- 

 deira, the Azores, or Cape Verds) existed in Europe in the Tertiary 

 period. Such are the native laurel, viburnum, and pine. The per- 

 sistence here of these ancient types speaks strongly for the constancy 

 of the climate — to-day a strong attraction to invalids — ^f or the aver- 

 age summer and winter temperature hardly differ ten degrees. 



The great age of the archipelago is further indicated by the 

 marked individuality of the flora of each island. The species have 

 had time to develop in various directions under the influence of the 

 different conditions to which they have been exposed, and the dif- 

 ficulty of obtaining foothold in the rocky, volcanic soil (pointed out 

 by Christ) has doubtless often prevented the intermixture of the 

 parent and derivative forms, so assisting in the formation of new 

 species. For it must have been only rarely that the seeds or fruits 

 brought from one island to another, or from the mainland, have 

 found themselves in places favorable to development. So species- 

 making has progressed, and as a consequence we find Teneriffe with 

 twenty-seven species known from no other region. Grand Canary with 

 seventeen, Palma with eleven, Gomera with ten, Hierro with three.* 

 Fuerteventura and Lanzarote, on account of their greater proximity 

 to the African coast, have a somewhat more continental aspect of 

 vegetation than the more westerly members of the group. They 

 have together thirty-two species which are either confined to them 

 or found very seldom on any of the other islands. Other peculiar 

 species are common to two or three islands only. 



The soil is very rich. With irrigation three harvests a year are 

 regularly gathered on Canary and Teneriffe. The water supply is 

 largely kept up by the cloud belts, which even in the driest seasons 

 form almost daily over the higher mountains, feeding the springs 

 there which are the life of the land. But, as has already been said, 

 the rocky, volcanic nature of the coast forbids the entrance of many 

 plants, and this fact has had great influence on the character of the 

 flora. The craggy hills and stony shores have a decidedly desert 

 aspect, and adaptations to drought in the form of fleshy, hoary, and 

 coriaceous leaves and stems abound. Euphorbias take the j)lace and 

 have the appearance of the cacti of American deserts. Eleshy 

 Crassulacece of the Sempervivum group are more abundant here 

 than in any other part of the world. There are twenty-two species 

 of them which are found nowhere else. Such fleshy plants are not 

 confined to the volcanic wastes and shores. They project from the 



* The number of peculiar forms on these two very fertile islands will doubtless be 

 increased when they are more thoroughly studied. 



