Botany and Zoology. 121 



ever, he chiefly rests on geological grounds. Regarded in this light, 

 the question will resolve itself, in the opinion of most botanists, into 

 one, concerning the power of migration, and the probability of migra- 

 tion having taken place, to a very great extent, over the Atlantic Ocean, 

 and against the prevailing direction of the winds. It may be contend- 

 ed that such a migration would have peopled these islands solely, or 

 mainly, with certain of the more transportable classes of plants; and 

 that the result must be, that the number of species belonging to each 

 natural order would be great in proportion to the facility with which 

 they bear transportation ; while only those orders could be numerous, 

 which possess that faculty in an eminent degree. But such are not the 

 characteristics of the Mediterranean plants found in Madeira. 



On the other hand, the existence of such a continent, during the pe- 

 riod when these islands bore the plants which they now produce, would 

 argue the former presence of ft very large Flora belonging to the type 

 which now distinguishes the islands in question from the Mediterranean, 

 and of whose previous existence the remaining species, peculiar to 

 them, are the indication. Against this theory it might be urged, that 

 more specific identity between the plants of the several insular groups 

 than now is seen, would then be the natural consequence ; for the af- 

 finity of vegetation between the different islands consists, not in identi- 

 cal species, but in representatives. The same agent, in short, which 

 effected the peopling of the several groups with the plants of conti- 

 nental Europe, would also have distributed more equally the non- 

 European species over the same area. 



It is, however, to the lofty peaks of Atlas that we must look, if any 

 where, for the continental representatives of those peculiar plants which 

 mark the North Atlantic Insular Floras. Thus, we expect to find the 

 productions of the Galapagos Archipelago on the higher levels of the 

 Urdillera; and the mountains of St. Thomas, Fernando Po and the 

 tameroons, on the west coast of tropical Africa, may yet exhibit to us the 

 botanical features of St. Helena. Outlying and high islands commonly 

 partake in the peculiar vegetation of a climate cooler than belongs to 

 ^ low lands of the adjacent continent; though, in the case of Juan 

 Fernandez, they sometimes exhibit genera equally isolated iu botani- 

 st affinities as their habitats are in geographical position. 



Tenerife.~The next point visited by the Niger Expedition, after 

 ! <*ving Madeira, was the Island of Teneriffe, where the vessel in 

 *h»ch Vogel had embarked remained but a few hours. The same 

 ? ^d, and the same port, Santa Cruz, had been touched at by the 

 Antarctic Expedition during the previous winter. Teneriffe is always 

 ™W to be classic ground by the naturalist, as the opening scene of he 

 *fcors of Humboldt, who there first appreciated in their full exte nt the 

 laws governing the Geographical distribution of plants. His lifelike 

 ftures of the natural phenomena, observed during an ascent of the 

 fijnous peak, have given an impulse to many succeeding scienti he trav- 

 ?«**, which has turned their thoughts and steps from closet «*« «£ 

 ** Pursuit of natural history at home, to seek far distant scenes, in 

 ^ West, the East and the South. '' . ^^ 



*** Peak itself is seldom descried : one hurried g *^*"™l 

 ■1**1 from upwards of sixty miles distance, was all we obtained . it 



B*W*» Series, Vol. IV, No. 10.— July, 1847. ^ 



