Cross- Breeding and Hybridizing. 17 



This fact was well expressed by Lindley a half century ago in the phrase, 

 " Hybridizing is a game of chance; played between man and plants." 



Bearing these fundamental propositions in mind, let us pursue the subject 

 somewhat in detail. We shall find at the outset that the characters of hy- 

 brids, as compared with the characters of simple crosses between stocks of 

 the same variety, are ambiguous, negative, and often prejudicial. The 

 fullest discussion of hybrids has been made by Focke, and he lays down the 

 five following propositions concerning the character of hybrid offspring : 



1 . " All individuals which have come from the crossing of two pure species 

 or races, when produced and grown under like conditions, are usually exactly 

 like each other, or at least scarcely more different from each other than 

 plants of the same species are." This proposition, although perhaps true 

 in the main, appears to be too broadly and positively stated. 



2. " The characters of hybrids are different from the characters of the 

 parents. The hybrids differ most in size and vigor and in their sexual 

 powers." 1 



3. "Hybrids are distinguished from their parents~by- their powers of vege- 

 tation or growth. Hybrids between very different species are often weak, 

 especially when young, so that it is difficult to raise them. On the other 

 hand, sross-breeds are, as a rule, uncommonly vigorous ; they are distin- 

 guished mostly by size, rapidity of growth, early flowering, productiveness, 

 longer life, stronger reproductive power, unusual size of some special organs, 

 and similar characteristics." 



4. " Hybrids produce a less amount of pollen and fewer seeds than their 

 parents, and they often produce none. In cross-breeds this weakening of 

 the reproductive powers does not occur. The flowers of sterile or nearly 

 sterile hybrids usually remain fresh a long time." 



5. "Malformations and odd forms are apt to appear in hybrids, especially 

 in the flowers." 



Some of the relations between hybridization and crossing within narrow 

 limits, are stated as follows by Darwin : " It is an extraordinary fact that 

 with many species, flowers fertilized with their own pollen are either abso- 

 lutely or in some degree steriie ; if fertilized with pollen from another flower 

 on the same plant, they are sometimes, though rarely, a little more fertile ; 

 if fertilized with pollen from another individual or variety of the same 

 species, they are fully fertile ; but if with pollen from a distinct species, they 

 are sterile in all possible degrees, until utter sterility is reached. We have 

 thus a long series with absolute sterility at the two ends — at one end due to 

 the sexual elements not having been sufficiently differentiated, and at the 



