416 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



there can be little doubt that the rosy-purple colour present in the 

 flowers and leaves of the various species of Cattleyu and Cypripedium 

 is due to the simultaneous presence of two complementary colour 

 factors, which we call C and E. If one or both of these factors is 

 absent, the result is a true albino, with no trace of purple sap in the 

 flowers and leaves. This purple colour can only be produced when 

 the two factors C and E are both present. 



Now, as we have just seen, the colour factors G and E may be 

 present in a double state — CO and EE — or in a single state — Cc and Er 

 • — or they may be absent altogether — cc and rr ; consequently no fewer 

 than five different kinds of albinos may exist, as follows: — 



For the sake of convenience it is usual in Genetics to represent 

 the presence of a factor by a capital letter and its absence by a small 

 one. 



These five albinos may be absolutely identical in appearance and 

 outward characters, yet each has a different germinal constitution, and 

 consequently will give different results in breeding. Each of these five 

 albinos will breed true to albinism when selfed, but when they are 

 crossed hiter se, different results will be obtained. Thus, out of the 

 fifteen possible matings, eleven will give all albinos, two will give on the 

 average equal numbers of albinos and coloured forms, one will give one 

 coloured form tO' three albinos, and one will give all coloured forms. 



Table I. gives the factorial details of these fifteen matings, showing 

 how the above calculations have been made. 



(1) CGrr 



(2) Ccrr 



(3) ccEE 



(4) ccEr 



(5) ccrr 



Table L— (Albino Matings). 



Parents 



Offspring 



Eesult 



(1) CCrr X (1) CCrr 

 (1) CCrr X (2) Ccrr 

 (1) CCrr X (3) ccRR 

 (1) CCrr X (4) ccRr 



(1) CCrr X (5) ccrr 



(2) Ccrr x (2) Ccrr 

 (2) Ccrr X (3) ccRR 

 (2) Ccrr x (4) ccRr 



All CCrr 



1 CCrr : 1 Ccrr 



All CcRr 



1 CcRr : 1 Ccrr 



AU Ccrr 



1 CCrr : 2 Ccrr : 1 ccrr 



1 CcRr : 1 ccRr 



1 CcRr : 1 ccRr : 1 Ccrr 



All Albinos 

 All Albinos 

 All Coloured 

 1 Coloured : 

 All Albinos 

 All Albinos 

 1 Coloured : 

 1 Coloured : 



1 Albino 

 3 Albinos 



1 Albino 



(3) ccRR X (4) ccRr 



(3) ccRR X (5) ccrr 



(4) ccRr X (4) ccRr 



(4) ccRr X (5) ccrr 



(5) ccrr x (5) ccrr 



(2) Ccrr x (5) ccrr 



(3) ccRR X (3) ccRR 



1 ccrr 

 1 Ccrr : 1 ccrr 

 All ccRR 

 1 ccRR : 1 ccRr 

 All ccRr 



1 ccRR : 2 ccRr : I ccrr 

 1 ccRr : 1 ccrr 

 All ccrr 



All Albinos 

 All Albinos 

 All Albinos 

 AU Albinos 

 All Albinos 

 All Albinos 

 All Albinos 



C represents first colour factor. 

 E represents second colour factor. 



