De Vries: ATavistic VARIATION IN OENOTHERA 79 
phylogenetically older than the linear ones, because they are the 
tule in the whole genus. But some authors suppose that from 
time to time there arise exceptions to the ordinary laws governing 
hybrids, and that such exceptions might be the source of many 
inconstant varieties and even of inconstancy in general. In this 
case the chance of getting such an exception by crossing would 
scarcely be greater than that of getting a mutation from the pure 
type. 
However slight these chances may be, I propose to try both 
ways and to see whether it would be possible to repeat the as yet 
doubtful and unknown original production of my O. cruciata varia. 
For there are not a great many cases in which the starting-points 
are to be had in so pure and so thoroughly controlled a state as 
in this instance. As to the question of the rule of the constancy 
of O. cruciata under cultivation, and of the hybrids, I hope to 
solve this in some years ; but as to the chances of getting excep- 
tions, it is evident that these are only small and that it would be 
preferable if the same experiments were made by a number of in- 
vestigators. 
The aim of such experiments would be to repeat artificially 
the production of QO. cructata varia and by this means to throw 
some light on its origin in particular and on the origin of incon- 
stant varieties in general. With a view to the possible repetition 
of this cross I will now give a description of the inheritance of the 
broad and linear petals in this variety. In so doing I limit myself 
to the detailed exposition of a single experiment carried on with 
the descendants of one original specimen of my variety. 
In the year 1897 this plant was raised from seed obtained in 
the usual way of exchange between botanical gardens. : I obtained 
but a single specimen, which bore all the characteristics of the 
typical O. cruciata. The spike, before the opening of the flowers, 
was placed in a bag of prepared parchment paper to prevent any 
visits from bees. The anthers touch the stigmas when opening, 
and the flowers fertilize themselves without any aid. In the epee 
way I always took care to collect each year purely pollinated 
seeds only, : 
This original plant bore but a few seeds, om which, during 
the next year I obtained only sixteen flowering individuals. But 
