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. The female of _muricata_ carries a group of features which he calls "_frigida_," and, though this is not quite explicitly stated in a definition of that type, it is to be inferred[6] that its characteristics are regarded as greater height, strong development of wood with comparative resistance to _Botrytis_, and broad leaves.