1912] STEVENS—HETEROSTYLOUS PLANTS 283 
he calls “‘caractéres hétérostyliques secondaires.”’ That is, the 
two forms differ not only in the parts of the flower, but also in the 
forms of the leaves. As he describes them (p. 229), the leaves of 
the long-styled form are “‘relatively longer and narrower, the ratio 
of the mean length (measured from the base of the petiole to the 
tip of the blade) to the maximum width being 2.86:1, and in plants 
grown in deep shade, 3.63:1”’; while the leaves of the short-styled 
form are ‘‘relatively wider and shorter, the ratio of the mean length 
to the maximum width being 2.41:1, and in plants grown in the 
shade, 3122127 
Relation of heterostyly to dioeciousness 
Dimorphic heterostylous plants present, in several respects, a 
striking resemblance to dioecious forms. In other hermaphrodite 
plants and in hermaphrodite animals, there is presumably unlimited 
possibility of crossing. In dimorphic heterostyled plants, however, 
the individuals are divided into two classes, which exist in approxi- 
mately equal numbers and are adapted for reciprocal fertilization, 
a condition essentially the same as that found in dioecious plants 
and in the higher animals. This resemblance is made still more 
evident by ERRERA’s recent discovery of differences in the vegeta- 
tive organs of the two forms in Primula elatior, comparable to the 
secondary sexual characters common in animals and found in a 
few dioecious plants, such as the hemp. 
Naturally, no very definite comparison can be drawn between 
the inheritance of heterostyly and the inheritance of sex until it 
is decided what laws the inheritance of sex actually follows. But 
it may at least be pointed out that the condition described by 
BATESON and Grecory for Primula sinensis, in which one form is 
a heterozygous dominant and the other a homozygous recessive, 
is exactly the condition believed, by several workers, to exist in the 
inheritance of sex, notably by Correns (4) for the dioecious 
Bryonia alba, and by Bateson for animals (Wilson 40, p. 63). 
Aside from any analogy with dioecious plants, fhe work of BATESON 
and GreGory on Primula sinensis indicates that in this form, at 
least, the inheritance follows the Mendelian law, a condition which 
indicates that a segregation of different characters occurs in the 
