MENDEL'S PRINCIPLES APPLIED TO ORCHID HYBRIDS. 615 



P. Spiccrianum and P. insigne, but according to Mendel's theory there 

 would be no determinants of the hybrid P. x Leeanum itself. 



This theory of Mendel is evidently quite different from anything that 

 has been advanced before, and if proved, will undoubtedly revolutionise 

 all previous theories of heredity. 



This in its turn would materially alter the present aspect of biology 

 towards Evolution. 



It is obvious that Mendel's theory of the purity of the determinants 

 can only be tested by experiment, and in Orchids it can be tested by 

 breeding from the hybrid P. x Leeanum or any other primary hybrid 

 and observing the results. 



Mendel tested his Pimm crosses in two ways only : firstly, by self- 

 fertilisation of the first crosses, and secondly, by re-crossing the first 

 crosses with one or other of their own parents. I have already carried 

 out these two experiments with the hybrid P. x Leeanum, but the results 

 have not yet come to maturity : nor is there, so far as I know, sufficient 

 material available at present to test the matter in these two ways. 



But, fortunately, we are by no means confined to Mendel's two 

 methods ; there are other ways open equally reliable as a test. One of 

 these is immediately available, and that is the crossing of the hybrid 

 P. x Leeanum with another species (distinct from its own parents), 

 namely P. Boxallii. 



During the past four years, forty-nine hybrids of P. x Leeanum $ 

 crossed with P. Boxallii $ , and vice versa, have flowered in my collection, 

 out of about sixty plants of that cross under raising, and these have given 

 a fair opportunity for the study and the practical application of Mendel's 

 theory. I may say in passing that there is no intrinsic difference 

 perceptible in the reverse cross. 



In accordance with the recognised rule for naming Orchid hybrids, 

 these secondary hybrids are all to be considered forms of the original 

 P. x Hera, raised by Messrs. J. Veitch & Sons, of Chelsea, in 1892. 



For the purpose of this paper the forty-nine individuals of P. x Hera 

 will be distinguished by the numbers given them in the order in which 

 they first flowered ; though a few of them have already received varietal 

 names on account of their horticultural merits. 



The accompanying photographs give a good idea of the flowers of 

 thirty-two of these hybrids which happened to flower together last 

 winter. It will be noted that the variation in these hybrids is remark- 

 able ; indeed, of the forty-nine already flowered no two are exactly alike, 

 and the extreme forms are very distinct indeed. With such a wide 

 range of variation in all the different characters of form and colour, it is 

 impossible to classify them with any pretence to scientific precision ; but 

 if we follow T Mendel's method and select a single character, we can then 

 group them easily. 



When I first examined these hybrids in the light of Mendel, I selected, 

 as the single character, the colour of the dorsal sepal of the flower ; as 

 this seemed to me to be the most conspicuous character, and probably 

 the most useful one from the practical point of view of the Orchid- 

 grower. 



But after a more detailed examination of the hybrids, their parents 



