ORIGIN OF SPECIES 621 
Vries observed in Oenothera Lamarckiana, they present some 
peculiar features, the chief of which are shown by the following 
comparisons. In none of his cases do specific attributes seem to 
have been complicated with varietal characters, unless one should 
except the case of O. manella. Perhaps a sufficient reason there- 
for is that most of the species of Oenothera have hitherto shown 
very little tendency toward variation. On the contrary, Lycoper- 
sicum solanopsis became divided into several varieties soon after 
its first mutation from Z. esculentum. 1 do not know in what 
variety it first appeared, but in the first of the two subsequent 
mutations, those which I observed, it appeared in a new variety, 
the Washington. Furthermore, in the next mutation, which was 
quite independent of the others, it appeared in the same variety. 
Indeed, in all the cases of specific mutation of Lycopersicum to 
which I have referred, some one horticultural variety seems to 
have been a conjunctive vehicle for the introduction of the new 
species, 
The scope of mutative action in Oexothera has been given in 
detail by Professor de Vries, but my observations show that in 
Lycopersicum the scope of that action is different in certain 
respects. He found mutation in Oenothera to act independently 
and separately upon the germ of each one of a very small number 
of seeds in an abundant fruitage of a large crop of plants; and 
that those seeds were usually subject, not to one and the same 
mutation, but to different specific mutations. I found in Lycoper- 
Sicum that one specific mutation acted completely and uniformly 
upon the germs of all the seeds, of all the fruits, of every plant of 
My crop of 1899, and that it acted in precisely the same manner 
in the crop of 1901. The suddenness of its action in the latter 
Crop especially, is shown by the fact that the Pennsylvania Acme 
seeds, planted in my garden in 1900, gave a full and uniform crop 
of true Acme plants; and that it was their seed which mutated 
So completely upun the same ground in 1901. In view of my 
Tepeated experience with the Acme variety one seems to be justi- 
in assuming that the determinate cause of mutation is now 
latent in every plant of that variety wherever grown, and that it 
quickly manifests itself when the flowering plants are brought 
under the influence of a favorable, exciting cause. 
