January, 1913-] 
THE ORCHID WORLF). 
«3 
THE APPLICATION OF GENETICS TO ORCHID 
BREEDING. 
By MAJOR C. C. HURST. F.L.S. 
{Continued from page 64.) 
The Remaking of a Blotched 
" Crispum." 
In 1 909 the writer showed that the 
"blotched " character in Odontoglossums 
behaved as a Mendehan dominant to the 
" plain " character which was recessive. Since 
then further evidence has given ample con- 
firmation. The logical consequences of this 
application of genetics to Orchid breeding 
lead one to support Mr. de Barri Crawshay's 
idea, expressed many years ago, that blotched 
" crispums " first appeared in a wild state 
through natural hybridisation with other 
species. 
From the point of view of genetics a 
dominant character is due to the addition of a 
factor, while a recessive character is due to 
the subtraction of a factor. A blotched cris- 
pum, therefore, consists in the addition of a 
factor to the ordinary typical plain crispum. 
The question arises, how was this dominant 
blotched character added to the typical plain 
crispum ? In order to illustrate the point we 
will take in hand the remaking of a blotched 
crispum by crossing an ordinary white " plain " 
crispum with one of the yellow blotched 
species that grows with O. crispum in 
Colombia, say O. luteopurpureum, the result 
will be, of course, the Fi yellow blotched 
hybrid, known as O. Wilckeanum, yellow 
being dominant to white, and blotched to 
plain. This natural hybrid appeared in 
importations before it was first raised in 
gardens. 
Next, we will re-cross this yellow blotched 
hybrid with another white plain crispum, the 
expected result as far as these two characters 
are concerned will be that in F2 out of four 
plants we shall get on the average one yellow 
blotched, one yellow plain, one white blotched, 
and one white plain. Among the white 
blotched forms will be found blotched 
crispums. There can be little doubt that is 
how the blotched crispums originated in a 
wild state by natural hybridisation. 
Other crossings might, of course, give the 
blotched crispum, but it seems more likely 
that it should originate from this particular 
cross than any other, on account of the 
natural distribution of these forms, as esti- 
mated by their frequency in importations. 
Further confirmation may be found in the 
fact that so far all the imported blotched 
crispums that have been bred from have 
proved to be heterozygous to the blotched 
character, giving plain forms when mated 
together. 
For instance, the blotched O. crispum 
Franz Masereel, O.-c. Leonard Perfect, O.-c. 
Lindeni, O.-c. Victona-Regina, O.-c. Rossen- 
dale, O.-c. Marias, O.-c. Lucianii, O.-c. 
Crawshayanum, and O.-c. Alphonso all give a 
few plain forms when mated witii other 
blotched forms, showing that each has only a 
single dose of the blotched character. This 
indicates that one of their parents was a plain 
crispum, otherwise some homozygous blotched 
forms would surely have turned up amongst 
them. 
The next step for Orchid breeders to take, 
therefore, is to breed these heterozygous 
blotched forms in^er se. On the average one 
out of three of the blotched forms produced 
in this way should be homozygous, or pure, 
with a double dose of the blotched character. 
These when bred from will give all blotched 
forms, whether mated with other blotched 
forms, or with plain forms. 
It will, of course, be understood that the 
blotched character in Odontoglossums is a 
very variable one, the blotches vary in size, 
form and number, while the pattern varies 
with the species used. It would be an inter- 
esting study to work out the several factors 
that are no doubt concerned in the different 
