Histoire Naturelk des lies Canaries. 481 
In these c< 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 granges masses en suivant une meme 
ligne de pente ; le regions que nous indiquons ne sont point des 
zones die vegetaux toujours regulierement superposees les unes aux 
autres, mais seulement de groupes partiels et isoles." 
And those tables of the geographical distribution of plants, divid- 
ing them into delined 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 Tisle 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- 
fr.ictuosites 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 grandiftoriim, 
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 Draccena draco. This plant, supposed to be 
