310 
rOrULAR SCIENCE REVIEW. 
there is a great predominance of individual varieties, while 
hybrid ovules impregnated by the pollen of pure species, give 
uniform products.”* Indeed, Wichura's experiments on 
willows have far more generally exhibited variety of form 
in the produce, when the pollen of hybrids was used ; and, on 
the contrary, uniformity where the pollen of pure species was 
employed. 
Now, Naudhts observations f on “ Hybridism considered 
as a cause of variability ” agree with this, for he shows that 
in hybrids of the second generation, there is a frequent and 
powerful tendency to “ sport irregularly so that from a single 
bed of a uniform type, intermediate between two parent forms, 
in the next year innumerable forms may appear ; while speci- 
fic characters have a tendency to be stable. Again : he lays 
it down as the first fact established that “ setting out from the 
second generation, hybrid vegetables, when fertile, revert very 
frequently to one of the two species from which they were 
derived ; some returning absolutely to one or the other form, 
sometimes suddenly, at other times slowly;” and he adds, that 
“ whole collections of individuals may be seen inclining to one 
side.” 
They do not, however, invariably revert. He gives the 
astonishing instance where offspring of Datura Icevis + ferox 
and of Datura ferox + Icevis differed most remarkably from 
the parent forms, although these reciprocal hybrids were 
all alike. Of the second generation he obtained twenty- 
six plants from D. Icevis + ferox , and nineteen from D. ferox + 
Icevis. In these two sets a most astonishing diversity of feature 
succeeded the former great uniformity. One only of D. Icevis + 
ferox reverted to D. Icevis. A very small number resembled 
D. ferox. Although it must be noted that seed of D. ferox and 
D. Icevis , 'pure, was sown in the same bed with the hybrids, 
the greater number of offspring resembled D. Stramonium 
and D. querci 'folia ! 
He cites Petunia nyctac/ ini flora + violacea, Linar ia purpurea 
+ vulgaris, as affording instances of ‘ • irregular variation.” But 
of the latter hybrid a good number of offspring reverted more or 
less to L. vulgaris, while a smaller number resembled L. 'purpurea. 
This irregular variation engenders only individual differences, 
and uniformity is not established between the descendants of 
hybrids except on the condition that they resume the normal 
livery of the parent species. Members of the third generation 
vary still more, but their variations are individual, and with no 
persistence. To be made permanent they must be grafted. 
* Journal of the Royal Horticultural Society (N. S.), Vol. I. p. 73, 1866. 
t Ibid. p. 1. 
