Darwin on the Effects of Gross- and Self- Fertilization. 129 



with twelve cases in which the crossed plants show no marked 

 advantage over the self-fertilized. There were, however, fifty- 

 seven eases in which the crossed exceeded the self-fertilized by 

 at least five per cent, generally by much more. 



Increase of vigor, as evinced in growth, appears generally to 

 be accompanied by increased fertility ; but sometimes the good 

 of crossing was manifested only in productiveness, i. e., in a 

 larger amount of seed. This proved to be the case in Esch- 

 sci,<Aiz;<i. in which— strange to say— self-fertilized plants of several 

 generations were superior in size and weight to inter-crossed 

 plants, even when the crossing was between flowers derived on 

 one side from American, on the other from English seed, from 

 which, upon Mr. Darwin's view, the maximum benefit should 

 be gained. This instance, however, stands alone. Yet it is 

 erl by several others, in a manner which might have 

 BBgatived the general conclusions of the research, if they had 

 been hastily gathered from a small number of trials. 



For example, in the sixth sell-; i of Ipomcea 



■purpurea, one of these plants took the lead of its competitor, 

 kept it almost to the end, and was ultimately overtopped only 

 by half an inch on a total height of several feet. To a>et rtain 

 whether this exceptionally vigorous plant would trai 

 power to its seedlings, several of its flowers were fertil 

 their own pollen, and the seedlings thus raised were put into 

 competition with ordinary self-fertilized and with inter-e !'<>-.-ea 

 plants of the .•i 1 rr.- 5 p..iM 1 'i.,._r generation. The six children of 



the ordinar e.netitors at the rate of 100 to 81, 



and the \w, rate of 100 to 9o ; and 



in the next generation the self- '•■} ren bea * 



those from a cross between two of the childrt i it t . . ' t 

 100 to 94. In the next generation the see. I 

 winter in a hot-house, became unhealthy, and the experiment 

 terminated w ,H, ,m in j k. .1 i*-ult -Moreover the remarkable 

 vigor of growth in Hero and its progeny wa- 



• 

 some utterly unknown cause, — a " ; \ m °* con " 



- transmitted to posterity, and ■:. 

 all the benefit of cross-fertilization, and somewhat more, both 

 as to vigor and fertility. A similar idiosyncracy made its ap- 

 ! ■ r . 



Discordant or anoi ' ■• s f m confusing, 



even though too few to l',-t se. ,u« the grand result of the 

 numerous experiments; but upon Darwinian principles in 

 which adaptations are ultimate results, they are to be expected, 

 as a consequence of the general and apparently vague pro- 

 clivity to vary. 



