426 JOTTENAL OF THE KOYAL HORTTCTTLTTTRAL SOOTETY. 



Tlie yellow ground colour in Odontogiossnms varies considerably in 

 shade according to the species and variety used. Some of the bright 

 yellow species are evidently heterozygous, or impure, carrying cream 

 recessive, as may be seen in some of the results of yellow x 

 white in certain primary hybrids where segregation into the two distinct 

 shades, cream and canary-yellow, is evident. When a pure white 

 ground appears in results of yellow x white, it is evidently due to 

 the impure nature of the wild yellow form used as a parent. 



The Making of a Scablet Grispum. 



A large number of interesting problems have already been taken in 

 hand by Orchid breeders, some of which bid fair soon to be successful, 

 though to the student of Genetics the results seem to be slow in coming 

 to hand. 



The question, for instance, of the making of a scarlet crispum by 

 combining the scarlet self-colour of CocliJioda Noezliana with the large 

 size of Odonioglossum crispum. The making of a scarlet Gattleya by 

 combining the scarlet self -colour of Sophronitis grandiflora with the 

 large size and broad segments of the species of the lahiata group of 

 Cattleyd. The making of a yellow Cattleya by combining the yellow 

 self-colour of Laelia Cowanii with the large size and broad segments 

 of the Cattleya. These and other problems equally interesting to 

 Orchid breeders are, judging by the results recently presented, now 

 well on the way to a solution. 



There is no doubt that the application of the principles of the Genetics 

 to these problems would not only help to hasten their solution, but 

 would also save much wastage of mistaken matings. In the three 

 particular problems noted above the first crosses in F^ all show a more 

 or less incom.plete dominance, both of the desired colour and size 

 characters. In other words, the single dose of each factor present in 

 the primary hybrid gives a different result from the double dose of each 

 factor present in the pure parents. Thus the double dose of the factor 

 present in the CochUoda, Sophronitis, and Laelia parents produces the 

 scarlet or yellow colour to perfection, whereas the single dose of the 

 factor present in the primary hybrids reproduces the scarlet or yellow 

 colour more or less imperfectly. 



The same thing happens in regard to the factor for size. The double 

 dose of the factor present in the Odonioglossum and the Cattleya parents 

 produces the large size desired, whereas the single dose of the factor 

 present in the primary hybrids does not. The simple solution of the 

 problem, therefore, lies in choosing the particular matings that will 

 give a double dose of each of the two characters that the Orchid breeder 

 wishes to combine, in these cases the scarlet or yellow colour and the 

 large size. It is obvious that this can be done by mating two of the F^ 

 hybrids together, and if the case is a simple one, as it appears to be, the 

 desired result should be secured in Fg, on the average in one plant out of 

 every sixteen raised. 



From this it will be seen that the common practice of mating the 



