Histoire Naturelle des lies Canaries. 481 



In these " climates" our learned authors remark, " Nous n'avons 

 valu presenter que la repartition des plantes sous le rapport des es- 

 peces qu'on rencontre par gran(!es masses en suivant une meme 

 ligne de pente ; le regions que nous indiquons ne sont point des 

 zones de vegetaux toujours regulierement superposees les unes aux 

 autres, mais seulement de groupes partiels et isoles." 



And those tahles of the geographical distribution of plants, divid- 

 ing them into defined limits, are considered as much too restricted, 

 and so lose their greatest value, unless the effects of local circum- 

 stances, exposure, &c come to be taken into the account. In fact, 

 that altitude and temperature are not the only circumstances which 

 have to be considered, or that the sort of established rule, " that 

 every 100 feet of height would lower the temperature 1° Reaum., and 

 was equal to 1° of distance from the pole," would depend in many, 

 if not in most instances, upon modifications entirely local. In illus- 

 tration of this, we may quote a paragraph which soon follows the 

 remarks on zonal vegetation. " Lorsqu' apres avoir parcouru les 

 vertes forets qui couvre une partie des versons du nord de Tene- 

 riffe, on tourne l'isle par la pointe la plus occidentale, les bois des 

 lauriers ne se retrouvent plus que dans le fond des etroites vallees 

 comprises entre le Cap de Zeno et le port de San-Jago. Quelque 

 groupes d'arbres forestiers garnissent encore, de ce cote, les an- 

 fractuosites les plus humides ; tandis que partout ailleurs ce ne 

 sont que pentes arides et nues. A mesure qu'on s'avouer sur le re- 

 vers meridional, le pays est encore plus devaste : la, plus de brises 

 rafraichissantes, plus de nuages ; mais le climat de la Mauritanie 

 meridionale avec la secheresse desesperante et son atmosphere de 

 feu." 



But amidst the varied vegetation of these islands, there are some 

 plants which defy a rule of confined distribution, " plantes vaga- 

 bondes," as they are graphically termed, which seem to delight in 

 no peculiar zone, and to belong to every climate. Among these 

 stragglers in Teneriffe, Pteris aquilina, Hypericum gratidiflorum, 

 and Erigeron viscosum, are widely scattered ; the two first appear 

 at from 1000 to 1500 feet of elevation, and are met with as high 

 as 7000 feet. Some plants which grow at a low elevation, are not 

 found for a long space, but appear again suddenly at some height, 

 thus Pancratium Canariense, growing on the shore of the Val-de 

 Guerra, appears again on the plateau of Trebejo, after an interval 

 of 3800 feet. 



Among the plants introduced to the Canaries, our authors are 

 unwilling to include the Dracaena draco. This plant, supposed to be 



