Before considering the possible meaning of these facts we must have in our minds the next and most novel of the recent extensions of knowledge as to the genetic properties of the _Oenotheras_. In the previous statement we have been concerned with the results of using either _Lamarckiana_ itself or one of its "mutants" _rubrinervis_, _brevistylis_, or _nanella_ as male, on one of the species _biennis_ or _muricata_. The new experiments relate to crosses between the two species _biennis_ and _muricata_ themselves.
1. That the reciprocal hybrids from these two species differed, _biennis_ × _muricata_ producing one type of F_{ 1} and _muricata_ × _biennis_ producing another. Each F_{ 1} resembled the father more than the mother.
2. That each of the hybrids so produced breeds true on self-fertilisation.
3. That if we speak of the hybrid from _biennis_ × _muricata_ as _BM_ and of the reciprocal as _MB_, then
gives exclusively offspring of _biennis_ type but that
gives exclusively offspring of _muricata_ type. Evidently, apart from all controversy as to the significance of the "mutants" of _Lamarckiana_, we have here a series of observations of the first importance.
The fact that reciprocal crossings give constantly distinct results must be taken to indicate that the male and female sides of one, if not of both, of the parents are different in respect of characters which they bear. This is de Vries's view, and he concludes rightly, I think, that the evidence from all the experiments shows that both _biennis_ and _muricata_ are in this condition, having one set of characters represented in their pollen-grains and another in their ovules. The plants breed true, but their somatic structures are compounded of the two sets of elements which pass into them from their maternal and paternal sides respectively. This possibility that species may exist of which the males really belong to one form and the females to another, is one which it was evident from the first announcement of the discovery of Mendelian segregation might be found realised in nature.[5]
_Oe. biennis_ and _muricata_ were crossed reciprocally with each other and with a number of other species, and the behaviour of each, when used as mother, was consistently different from its behaviour when used as father. De Vries is evidently justified by the results of this series of experiments in stating that the "Bild," as he terms it, or composition of the male and female sides of these two species, _biennis_ and _muricata_, are distinct. On the evidence before us it is not, however, possible to form a perfectly clear idea of each, and until details are published, a reader without personal knowledge of the material cannot do more than follow the general course of the argument. For fuller comprehension a proper analysis of the characters with a clear statement of how they are distributed among the several types and crosses is absolutely necessary. According to de Vries the female of _biennis_ possesses a group of characters which he defines as "_conica_" in allusion to the shape of the flower-buds. Besides the conical buds, this group of features includes imperfect development of wood, rendering the plant very liable to attacks of _Botrytis_, and comparatively narrow leaves.