ON HYBRIDIZATION AMONG PLANTS. 
309 
which are produced ; are they proportionate to the apparent 
affinity of the two species ? — Generally, yes.” But many 
examples can be given where closely-allied species refuse to 
cross, where more distant affinity proves no barrier. Dean 
Herbert has shown this in the cases cited above, of Hippeas- 
trum, Zephyranthes, &c., and remarks that the production of 
any intermixture, whether fertile or not, gives reason to sus- 
pect that the parents were descended from one common stock, 
i.e.f referable to one (natural) genus. And he gives it as his 
opinion, that the facility of crossing plants depends, therefore, 
more upon their constitution, and we would add “idiosyncracy,” 
than upon their so-called morphological affinity. M. Naudin 
concludes his remarks with the following words 
The aptitude of species to fecundate each other reciprocally, and the 
degree of fertility of the hybrids which spring from them, are truly the sign 
of special affinity considered with reference to their origin ; and, in the 
majority of cases, this affinity is indicated by an exterior organization — in a 
word, by the physiognomy of the species. 
4. The Physiognomy of Hybrids. — We must observe the first 
and second generations to gain a correct idea of the aspects 
presented by hybrids. There is generally admitted to be a 
great uniformity in the members of the first generation. They 
resemble each other as much as the offspring of legitimate 
species; and this holds good with “reciprocal”* hybrids. 
Though they are intermediate in character between the parent 
forms, yet the hybrids may approach more nearly the form of 
one parent than the other, or partake of both forms in different 
groups of their organs ; thus, Mirabilis longiflora + jalapa is 
more like M. longiflora in its vegetative organs, but more re- 
sembles M. jalapa in its flowers. 
M. Naudin denies RegePs assertion that hybrids sprung from 
species far apart, or, from genera, are more like the male 
parent ; and he cites Datura Stramonium + ceratocaula as 
an example, which more nearly resembled the former, or 
female type. This predominance of one form in the hybrids 
he, as also Gaertner, believes due to the prepotent influence of 
one species over another ; Wichura, however, never saw a pre- 
potent type in willows, at least, as far as the first generation 
would exhibit it, for he observes that double or “ reciprocal ” 
crosses are exactly alike. 
“ Wichura confirms Gaertner in the assertion that where 
hybrid pollen is used for the impregnation of simple hybrids, 
* By reciprocal hybrids are meant, those which are obtained by using the 
pollen of each of the two plants for the stigma of the other respectively. 
