24 BOARD OF AGRICULTURE. [Pub. Doc. 



If, therefore, the philosophy of sex is to promote variation 

 by the union of different individuals, it must follow that 

 greatest variation must come from parents considerably 

 unlike each other in their minor characters. Thus it comes 

 that in-breeding tends to weaken a type, and cross-breeding 

 tends to strengthen it. And at this point we meet the par- 

 ticular subject which I am to present to you. I have intro- 

 duced you to this preliminary sketch because I contend that 

 we can understand crossing only as we make it a part of the 

 general philosophy of nature. There are the vaguest notions 

 concerning the possibilities of crossing, some of which I hope 

 to correct by presenting the subject in its relations to the 

 general aspects of the vegetable world. 



We are now prepared to understand that crossing is good 

 for the species, because it constantly revitalizes offspring 

 with the strongest traits of the parents, and presents ever- 

 new combinations which enable the individuals to stand a 

 better chance of securing a place in the polity of nature. All 

 the further discussions of the subject are such as have to do 

 with the extent to which crossing is possible and advisable, 

 and the mere methods of performing the operation. 



At this point I must digress, for the purpose of defining 

 certain terms which it is necessary to use frequently. I use 

 the term cross to denote the offspring of any sexual union 

 between plants, whether of different species or varieties, or 

 even different flowers upon the same plant. It is a general 

 term. And the word is also sometimes used to denote the 

 operation of performing or bringing about the sexual union. 

 There are different kinds of crosses. One of these is the 

 hybrid. A hybrid is a cross between two species, as a plum 

 and a peach, or a raspberry and a blackberry. There has 

 lately been some objection urged against this term, because 

 it is often impossible to define the limitations of species, — 

 to tell where one species ends and another begins. And it 

 is a fact that this difficulty exists, for plants which some 

 botanists regard as mere varieties others regard as distinct 

 species. But the term hybrid is no more inaccurate than the 

 term species, upon which it rests ; and, so long as men talk 

 about species, so long have we an equal right to talk about 

 hybrids. Here, as everywhere, terms are mere conveniences, 



