338 CHAPTERS ON EVOLUTION. 



a part of organic nature, we may feel perfectly justified in supposing 

 that the conditions and results which cross-fertilisation tends to 

 evoke and produce, will harmonise in their tendency and direction 

 with the course of events through which the living universe has 

 been and is being moulded, developed, and evolved. 



To the question, " Why does cross-fertilisation appear to be 

 favoured by nature over self-fertilisation? " a plain reply is at hand in 

 a comparison of ihe results which accrue from each of these 

 processes. Mr. Darwin's laborious researches on the comparative 

 fertility of various species of plants when self- fertilised and cross- 

 fertilised, supply an answer to the foregoing question, by showing that 

 in every respect the cross-fertilised flowers yield more seeds, and 

 give rise to a stronger and more numerous progeny than the self- 

 fertilised. The reader who consults Mr. Darwin's " Forms of 

 Flowers " will find himself supplied with ample data in proof of the 

 advantages of cross-fertilisation. In the primrose, for instance, when 

 short-styled and long-styled flowers were crossed in what Darwin 

 calls "legitimate union," the result was invariably to produce a larger 

 number of seeds than when each form was fertilised by its own 

 pollen. Out of 12 long-styled primroses fertilised by short-styled 

 poHen, !! good capsules (or ripe pistils) were produced, with an 

 average of 66^9 seeds per capsule; whilst 21 long-styled flowers, 

 fertilised by long-styled pollen, produced only 14 capsules, with an 

 average of 52^2 seeds per capsule. The cowslip gave a similar result ; 

 and the tendency towards greater vigour of offspring when cross- 

 fertilisation is employed, appears to be of the most general kind. In 

 some plants, indeed, cross-fertilisation is absolutely essential for the 

 mere continuance of the race ; so that this method of seed-production 

 is not merely accidental or advantageous, but absolutely necessary 

 for the continuance of the race. Most of the orchids illustrate this 

 state of -matters. The presence of humblebees is well-nigh an 

 absolute necessity for the continuance of the heartsease ( Viola 

 tricolor]} and the well-known case of the clovers may be cited as 

 highly characteristic of the benefits developed through cross- 

 fertilisation. Twenty heads of Dutch clover, protected by Darwin 

 from bees, yielded no seeds : whilst twenty heads growing exposed as 

 in a stare of nature, yielded 2,290 seeds. One hundred heads of red 

 clover protected from bees were absolutely sterile ; a second hundred 

 exposed yielded 2,700 seeds. The scientific demonstration of the 

 interdependence of living beings becomes in this fashion perfectly 

 clear. Carried out to its ultimate results, such demonstration 

 becomes' sufficiently startling. British brain and sinew depend 

 (according to a foreign estimate) on home-fed beef; whilst the quality 

 of that nutriment is said to be dependent upon the clover on which 

 the ox subsists. But clover owes its continuance to humblebees ; 



