340 
LOCK : STUDIES IN PLANT BREEDING 
male parent much intensified. The pods showed spots and 
flecks of purple on a green basis. 
Now a tall form of Phaseolus vulgaris grown by natives in 
Ceylon shows just these same characters of flowers, seed, and 
pod-colour, and this variety has a distinctly primitive and 
relatively unimproved appearance. It therefore seems likely 
that this was a true case of atavism on crossing in the strict¬ 
est sense. Unfortunately all the offspring of the cross-bred 
plants were killed by drought before the flowers appeared, 
and I have not yet been able to repeat the experiment. 
In one of the crosses described by Tschermak a race of 
Pisum arvense with i4 rose-coloured ” flowers crossed by cer¬ 
tain white-flowered races of Pisum sativum yielded in F x 
plants with exclusively “ red ” flowers, like those of the 
ordinary Pisum arvense. 
In F 2 . Tschermak found the proportion red : rose : white 
to be 239 : 75 : 83 : and in several other cases of similar crosses 
the ratio 9:3:4 was approached ; i.e., coloured : white — 
3 : 1 according to the Mendelian expectation ; and also among 
the coloured forms ; reversionary : coloured parental — 3:1. 
Tschermak supposed the red colour to have existed as a 
latent rudiment in the rose-flowered parent, and that it was 
rendered evident on crossing ; and he applied to the pheno¬ 
menon the term Cryptohybridism. The character which 
thus suddenly appears he described as cryptomeric. Simi¬ 
larly Tschermak crossed a race of Pisum arvense having no 
purple spots on the yellowish green testa with a white- 
coated race of Pisum sativum. In Fj purple spots appeared 
in all the offspring. In F 2 appeared : purple spotted seeds, 
coloured seeds without purple spots, and white seeds ; doubt¬ 
less in the same proportion. This series is identical with the 
offspring of the cross purple sugar pea by native yellow 
described above (p. 331), and there can be little doubt that a 
similar explanation in terms of gametes can be applied to it.* 
* I received Tschermak’s Paper in February just as these plants (F^) were 
being 1 gathered in. 
