78 DE Vriss: ATAVISTIC VARIATION IN OENOTHERA 
tation, in the same way as many of our ordinary varieties of gar- 
den plants have been produced, the other is by crossing, which is 
perhaps a still more common source of new garden varieties. 
Both possibilities seem to me to be of some interest, since they 
bear directly on the great question of the internal causes of incon- 
stancy in general. For in my variety the petals do not vary ac- 
cording to Quetelet’s law, about a mean, which lies somewhere 
between the obcordate and the linear form, producing petals of 
which the majority do not essentially differ from this mean, whilst 
the extremes are very rare. . Quite on the contrary, the obcordate 
and the linear petals seem to be two alternating types only united 
- by rare intermediate steps. 
In case my variety originated by a mutation, we would there- 
fore have an imperfect one, producing the new type only in part of 
the individuals and remaining true or returning to the pure form of 
Ocenothera cruciata in the others. In many points this case would 
be analogous to that of Oenothera scintillans, which originated in 
my garden from O. Lamarckiana, but which, though artificially 
pollinated with its own pollen, returns in each generation in often 
a relatively large, part of the individuals to the original type. 
In case my variety originated by a cross, it should first be re- 
marked that the supposed hybrid is not intermediate between 0. 
cruciata and some allied species, but that it has, as far as I can 
judge, all the characters of the former, the constancy in the form 
of the petals excepted. I have endeavored to show in my “ Mu- 
tations-theorie”’ (Part II., p. 100) that O. muricata is probably the 
only species which could have given such a hybrid with the 0. 
crucitata, Now it is clear that having once obtained seeds from 
the original and constant O. cruciata, 1 possess the materials to 
bring about this crossing and also those with other allied species, 
and to try whether it will be possible to get an inconstant hybrid 
in this way. I propose to do so, but from what I know of my 0. 
cruciata varia and of the hybrids I have made of it with more than 
one other species, it is very improbable that the hybrid O. cruciata 
x O. muricata will be as a rule inconstant. It is far more probable 
that it will exhibit the dominant character, which must be the broad 
petals, and either give a constant progeny with this feature or split 
up according to Mendel’s laws. I take the broad petals to be 
