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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



MENDEL'S PRINCIPLES APPLIED TO ORCHID HYBRIDS. 

 By Charles C. Hurst, F.L.S., F.R.H.S. 



(Second Paper.) 



In the first paper (vol. xxvi., pp. 688-695) I endeavoured to show the 

 value of Orchid hybrids for observations in heredity. 



As an illustration of this I gave the results of analyses of the inherit- 

 ance of 4,548 pairs of specific characters in the first generation, in 

 accordance with the methods adopted by Mendel, and detailed in his 

 remarkable paper, a translation of which was given in the Society's 

 Journal, vol. xxvi. p. 1. 



As a result of these observations, the following may be laid down as 

 a general rule : — 



That in Orchid hybrids of the first generation single specific cha- 

 racters are inherited in all degrees of blending ; forming, on the whole, 

 a perfect series between the respective characters of the two parents. 



This result in Orchid hybrids differs materially from that obtained by 

 Mendel in his first crosses with races of Garden Peas. 



In Mendel's experiments one parental character always proved 

 dominant over the other one, giving no intermediate forms. The reason 

 of this apparent discrepancy can, I think, be easily explained on the basis 

 of the difference between specific and racial characters. But as the 

 question of dominance or intermediacy in the first generation is only of 

 secondary importance, I will leave its discussion for the present, and at 

 once proceed to that more vital question, the separation of characters in 

 the second generation. 



From both the biological and the practical points of view, the most 

 important and far-reaching result of Mendel's experiments is the brilliant 

 .speculation by means of which he explained his practical formula for 

 the separation of characters in the second generation. 



Mendel's theory may be briefly described as follows : — 



That the determinants of each single character in the germ-cells of 

 hybrids {both pollen and egg-cells i are pnre and not hybrid in their 

 nature : representing alternately the respective character either of the one 

 parent or the other of the hybrid, but not both. 



For instance, the hybrid Orchid Paphiopcdilum x Leeanum is the 

 product of the two species P. Spicerianum and P. insigne. 



According to Mendel's theory, the germ-cells of P. x Leeanum will 

 not contain hybrid determinants for any single character, but one germ- 

 cell will contain determinants of pure P. Spicerianum for that character, 

 while another germ-cell will contain determinants of pure P. insigne for 

 that same character ; the process being apparently according to the law 

 of chance. 



Of course, when all the single characters are taken into account 

 together, each germ-cell would naturally contain determinants of both 



