26G REVIEWS. 



stated, are hypothetically regarded as degraded from higher 

 iloral types. 



We are bound to glance at some of the considerations 

 which arc adduced in support of this thesis. They are multi- 

 farious and of unequal value. As has occurred in other cases, 

 so here also, the weightiest objections to Mr. Darwin's view 

 are those which he has himself brought out, namely, the fact 

 that, as tested experimentally under cultivation, while some 

 plants are much increased in vigor and fertility by artificial 

 intercrossing, others are not sensibly benefited ; and that the 

 benefit derived in marked cases is not cumulative, but reaches 

 its maximum in two or three generations. And even close 

 breeding under cultivation occasionally gives rise to very 

 vigorous and fully prolific self-fertile races. Then many 

 plants are fully self-fertile in nature, and it is not proved that 

 any such have lost or are in the way of losing either fertility 

 or vigor through continued inter-breeding. But, before draw- 

 ing from this the conclusion that cross-fertilization is of little 

 or no account in nature, it should be remembered that bud- 

 propagated races are in similar case. Races exist which have 

 been propagated only from buds for hundreds of years, with 

 seemingly undiminished vigor, and there is no proof that any 

 one has succumbed under the process. But for all that we 

 do not doubt that sexual reproduction contributes something 

 to the wellbeing of the species, besides facilitating its disper- 

 sion. Again, no one questions the necessity of fertilization 

 by pollen to the production of embryo in the seed ; yet, even 

 in this, the necessity is not so imminent but that some em- 

 bryos may originate without it. 



In short, the facts brought out by Darwin and others, and 

 all the considerations of the present essays, are best har- 

 monized by the conception which the former has consistently 

 maintained, namely, that an occasional cross suffices to secure 

 the benefit of intercrossing, whatever that may be. Nothing 

 vet appears which seriously disturbs our conviction that just 

 this is what nature generally provides for. 



Mr. Henslow's proposition, " The majority of flowers are 

 self-fertile," is doubtless true in the sense that they are capa- 



