CHTGIX OF PLANTS. 217 



tlie consideration of the experience argument, to remark a few 

 incidental, but by no means unimportant, consequences of 

 the belief. And, fii-st, let him weigh for a moment the com- 

 parative demands on his credulity of the theory by which 

 Professor Forbes accounts for the various floras of the British 

 islands, and that hypothesis of transmutation which the 

 author of the " Yestiges" would so fain put in its place, as 

 greatly more simple, and, of course, more in accordance with 

 the principles of human belief. In order to the reception of 

 the Professor's theory, it is necessary to hold, in the first place, 

 that the creation of each species of plant took place, not by 

 repetition of production in various widely-separated centres, 

 but in some single centre, from which the species propagated 

 itself by seed, bud, or scion, across the special area which it is 

 now found to occupy. And this, in the first instance, is of 

 course as much an assumption as any of those assumed num- 

 bers or assumed lines with which, in algebra and the mathe- 

 matics, it is necessary in so many calculations to set out, in 

 quest of some required number or line, which, without the 

 Uvssistance of the assumed ones, we might despair of ever find- 

 ing. But the assumption is in itself neither unnatural nor 

 violent ; there are various very remarkable analogies which 

 lend it support ; the facts which seem least to harmonize with 

 it are not wholly irreconcil cable, and are, besides, of a merely 

 exceptional character ; and, further, it has been adopted by 

 botanists of the highest standing.* It is necessary to hold, 



* The following digest from Professor Balfour's very admirable 

 ** Manual of Botany," of what is held on this curious subject, may be 

 not unacceptable to the reader. "It is an interesting question to de- 

 termine the mode in which the various species and tribes of plants were 

 originally scattered over the globe. Various hypotheses have been ad- 

 vanced on the subject. Linnseus entertained the opinion that there was 

 at first only one primitive centre of vegetation, from which plants were 

 distributed over the globe. Some, avoiding all discussions and difficul- 

 ties, suppose that plants were produced at first in the localities where 

 they are now seen vegetating. Others think that each species of plant 



