THE ORCHID REVIEW. 45 



EXPERIMENTS IN PLANT HYBRIDISATION. 



Your interesting review of Mendel's law of the separation of characters in 

 crosses (p. n), prompts me to send you a note on one special feature of 

 Mendel's experiments upon which the whole question depends. The cen- 

 tral principle of Mendel's law is that it deals solely with a single character 

 at a time: it consequently ignores the individual plant which is made up of 

 a large number of single characters. Given the law for a single character, 

 the determination of the individual is simply a matter of calculation accord- 

 ing to the calculus of chance. A practical illustration will perhaps show 

 this important point more clearly: — 



I suppose it would be a desirable thing to be able to raise a number of plants 

 of Paphiopedilum Fairrieanum true from seed, and your reviewer suggests 

 that the hybrids of P. Fairrieanum might be self-fertilized to gain this 

 object, in accordance with Mendel's law. But this would not be so easy as 

 it seems. According to Mendel's law, by raising four seedling plants from, 

 e.g., P. x Arthurianum fertilized with its own pollen, one ought, on the 

 average, to raise one plant bearing any single character, e.g., the recurved 

 petals, of P. Fairrieanum. Bnt this would not be sufficient for the practical 

 hybridist : he would want to raise P. Fairrieanum true in its many charac- 

 ters, both in form and colour. To do this, e.g., in sixteen conspicuous charac- 

 ters (which would probably be sufficient for all practical purposes), the 

 hybridist would have to raise, on the average, no less than 510 plants before 

 he got a " Simon Pure." Of course one might get it true the first time, 

 but the chances would be 510 to 1 against it. (In parenthesis, I might say 

 that judging from my own experience with other species, one would be 

 likely to get the same result much quicker by raising ten plants or less of, 

 say, P. x Arthurianum crossed with P. Fairrieanum, if pollen of the latter 

 can still be obtained). Hence one sees the absolute necessity of testing 

 Mendel's law by single chara2ters only, and not by an individual made up 

 of many characters. This probably explains the apparent intermediate 

 state of many self-fertilized hybrids, some of the characters being inherited 

 from one ancestral species, some from the other, and others again blended 

 between the two. This is in strict accordance with Mendel's formula 

 A + 2A« + a where A and a respectively represent the character in the 

 two ancestral species. 



I trust that our hybridists will act upon the good advice of the reviewer 

 and fertilize any easily raised primary hybrid between two distinct species, 

 that may be in flower, with its own pollen. For my own part, I would be 

 very pleased to receive a flower of each of the seedlings raised therefrom 

 for analysis. We should then be able to test Mendel's law in a practical way. 

 Burbage Lodge, Hinckley. C. C. Hurst. 



