466 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



in which this method was tried have been given in an earlier 

 account.* 



We reach this point then, that in so far as the views here discussed 

 are not based on the fundamental fact which we must now regard as 

 established, viz. that the single or double nature of the future Stock 

 flower is already determined at the moment of fertihzation, and, like 

 other inherited characters, is laid down in the seed, v/e need not concern 

 ourselves further with them. The suggestion that this might be found 

 to be the true explanation had been thrown out earlier by OBERDiECKf 

 (1879), and is again mentioned later by GoebelJ (1886), but proof was 

 lacking, the position hitherto being rather of that negative order that 

 where every other suggestion had failed, possibly this one might be 

 true. As soon as breeding tests were applied, however, it became 

 evident that the production of doubles was a regular and orderly 

 phenomenon. The Mendelian method of analysis — the essence of 

 which is to investigate, not strains as a whole, however homogeneous 

 they may appear to be, and not collections of individuals, however 

 small, but each particular individual separately — provides us with a 

 means of elucidating the real conditions upon which the appearance 

 of doubles depends, and thus explains the perplexing behaviour of the 

 Stock in regard to this character. 



In the first place it must be understood that in the two cultivated 

 Stock forms incana and annua there are to be found among the popu- 

 lations in our gardens to-day, not merely singles and doubles, but 

 two fundamentally distinct types of singles. As I conceive it, there 

 must have arisen some two hundred and fifty years back at least, 

 and possibly longer ago, from what cause we do not know, a new type 

 of single, not differing in outward appearance in any way from the 

 ordinary individuals of the species, but having a different gametic 

 constitution — a constitution that resulted in the production of ovules 

 and pollen grains of a different character from those of the original 

 ordinary single. By some process of evolution the species thus became 

 heterogeneous, and as a direct result of this variation there arose the 

 double — a form constantly thrown by the new type of single, which is 

 therefore termed ever-sporting, in contrast with the original type, which 

 is pure-breeding. Thus we arrive at a species having as constant type- 

 elements the following forms : — 



1. Singles, whose gametic constitution is such that their posterity 



in all succeeding generations are single also. 



2. Singles, whose gametic constitution is such that they yield a 



mixture of doubles and singles, the doubles being in a sHght 

 majority and altogether sterile, the singles in each succeeding 

 generation giving again a mixture of singles and doubles. 



3. Doubles, which, as stated, are incapable of producing offspring. 



* See Saunders, Journal oj Genetics, vol. i. No. 4, p. 366, 1911. Also Journal 

 Roy. Hort. Soc. vol. xxxviii. p. 481. 

 t loc. cit. 

 t loc. cit. 



