96 Reversion in Orchids [ch. 



call "plum," and a dilute form of red which is known as 

 *' copper," &c. Any of these colours may be on a white 

 ground, or on a cream ground '^. 



Albino Orchids giving Coloured F^, 



In Orchids a series of facts has been observed which 

 are exactly comparable with those described in the Sweet 

 Peas and Stocks. There are several albino orchids in the 

 genus Cypripedium. Of these some when crossed together 

 give coloured offspring, and others crossed together give 

 albinos only. Mr Hurst t most kindly furnished me with a 

 complete list of the results of crossing albino Orchids so far 

 as they have been published. This list covers a very wide 

 range of cases to which no reference can be made here. As 

 regards Cypripedium most of the experiments were made 

 by Mr N. C. Cookson of Wylam. I am much indebted to 

 him and to his gardener Mr H. J. Chapman for information 

 about them. For example : 



C, callosum Sanderae x C. bellatulum album gives all 

 offspring coloured (25 plants bred by Mr Cookson). 



C Lawrenceanum Hyeanum. x C, bellatulum alburn^ all 

 offspring coloured (Cookson). 



On the other hand 



C Lawrenceanum Hyeanum> x C callosum Sanderae 

 gives offspring all albinos (viz. C. ^' Matidiae'') (raised 

 by Messrs Charlesworth and independently by Baron 

 Schroder). 



If therefore we suppose that bellatulum album is carrying 

 one of the complementary factors, say C, and that the other 

 factor R is present in callosum Sanderae and in Lawre^ice- 

 anum Hyeanum^ the results are correctly and consistently 

 represented. 



As regards the behaviour of the pure types however there 

 is one occurrence to be recorded which cannot be explained. 

 Of the albinos named above, one, callosum Sanderae has been 

 self-fertilised and gave albinos only, as must be expected. 



* Though all the various combinations occur it is probable that the 

 distribution of white and cream is by no means a simple one, but the 

 analysis of the inter-relationship between white and cream has not yet 

 been worked out completely. 



t See also Hurst, Gard. Chron, Feb. 6, 1909, p. 81. 



