18 Mr. R. B. Hinds on Geographic Botany, 



what may not be expected from plants, even though assisted by 

 a favourable structure ? Among these plants instances may be 

 found which enjoy a very contracted habitat ; Carduus cyanoides 

 is one of these, and is found on two spots only in Germany. 

 This plant has attached to its seed-vessel a brush of bristly 

 hairs, like many other of its congeners, the use generally as- 

 signed to which is to assist diffusion, and which it often admira- 

 bly accomplishes, though not in the present instance. 



Numerous instances are related of seeds being carried by cur- 

 rents on the swell of the ocean across extensive seas from tropi- 

 cal coasts to the shores of northern countries. Fruits have often 

 been picked up on the coasts of Scotland, Denmark and Sweden, 

 which there is not the least doubt were shed within the tropics. 

 Nor does the sea-water in all cases destroy the power of germi- 

 nation, as plants have occasionally been reared from them in our 

 own country, and on the sandy beaches within the tropics the 

 seeds of Mucuna pruriens are sometimes found in quantities in 

 active germination, yet washed about by every rising tide. A 

 more powerful agent has been man, who in his migrations has 

 spread a number of plants in every place where he has fixed his 

 residence ; the proportion of these to the flora is however small, 

 and they have seldom given a character to the vegetation*. It is 

 therefore only in a few cases that it can be admitted plants have 

 been thus diffused; the mass of vegetation has not moved over 

 the world by this or similar methods. 



A slight inspection of the tracery on a globe exhibits a certain 

 relation in the distribution of water and dry land : towards the 

 north a mass of land occupies the Arctic circle extending around 

 the pole ; traversing the globe on all sides towards the equator, 

 divisions in the surface are gradually observed, increasing in size 

 as they descend, and when arrived within the tropics, mostly en- 

 larged into seas and oceans. The intervals between the masses 

 of land beyond the equator more resembling processes shooting 

 into the ocean, still increase, and towards the south are lost in a 

 vast encircling sea. The tropical portions of each of the great 

 divisions of the world are nearly isolated, whilst in the northern 

 regions the consolidation is considerable, and the whole admits 

 of a comparison, perhaps rather a rough one, of the manner in 

 which the spread fingers are united at their base to the palm of 

 the hand. In each of the divisions the vegetation of the tropics 

 is rich and varied, but the identity in the productions of one with 



* At Valparaiso in Chili, among a vegetation where they were in every 

 respect strangers, I found the following plants: — Linum catharticum ; Son- 

 chus oleraceus ; Polygonum persicaria ; Geranium molle, G. dissectum ; 

 Rumex pulcher ; Mentha pulegium ; Viola odorata ; Equisetum palustre. 

 Similar instances are frequently mentioned in the writings of travellers. 



