(^88 



JOUENAL OF THE EOYAL HORTICULTURAL SOCIETY. 



MENDEL'S " LAW " APPLIED TO ORCHID HYBRIDS. 

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

 (First Paper.) 



Mendel's formula, for the separation of characters in crosses, was first 

 enunciated in 1865 (Nos. 17-19).* Since that time it appears to have 

 been lost in obscurity, until brought to light by the researches and 

 experiments of Prof. Hugo de Tries, early in 1900. (Nos. 8-12.) 



De Vries' experiments confirmed Mendel's formula in many widely 

 difterent genera, including Agrostem7na, Clielidonium, HyoscyamuSy 

 Lyclinis, (E7iothera, Paimvcr, Zca, Aster, Chrysanthemum, Coreopsis, 

 Solanum, Veronica, Viola, Clarkia, Silene, Datura, and Trifoliwn. (Nos. 

 8-12.) 



Soon afterwards some of Mendel's original experiments with Peas 

 were repeated and confirmed by both Correns (Nos. 8-7) and Tschermak 

 (Nos. 20-22). (See also Bateson, Nos. 1-2.) 



Mendel's formula may be simply stated as follows : — If two distinct 

 but corresponding characters, A and a, be united by crossing, and the 

 resulting crosses be self-fertilised, the progeny as regards this pair of 

 characters will separate themselves according to the formula A4-2Aa + a. 

 That is to say, on the average, out of every four plants raised, one will 

 take after the original character A, two will be intermediate Aa, and one 

 will take after the original character a. In other words, one-half will 

 retain the original characters, and one-half will be intermediate. This, 

 formula of Mendel, having been confirmed by three independent observers 

 and extended to no fewer than sixteen distinct genera, is evidently of 

 great importance. 



The next question is. How far can Mendel's formula be extended to 

 other genera and to other kinds of crosses '? 



With regard to this, a careful study of the above experiments suggests 

 the folloVing observations : — 



(1) Racial characters alone have formed the basis of all the experiments^ 



(2) Pairs of distinct though corresponding characters are dealt with 

 as separate units, while the individual plant, made up of many characters^ 

 is ignored. 



(3) Each character of the pair is not only distinct from the other, but 

 seems to be antagonistic to it ; for in each pair one character has in all 

 the experiments been dominant in the first generation, to the exclusion 

 of the other, i.e. the recessive one, which latter does not show itself until 

 the second generation. 



(4) The dominant character has in all cases been the older and typical 

 one, the recessive character being recently descended from the dominant 

 one. 



We may therefore, I think, fairly conclude that, as far as the first 

 generation is concerned, the experiments of Mendel and others mentioned 

 * The Nos. refer to list of Authors on p. 694. 



