W. Travers.—Hybridization of Plants. 33 
belonging to the one or the other, in order to resume a normal homogeneous 
structure ; whilst this tendency would, as it appears to me, be most readily 
and successfully ministered to by fertilizing the ovule of the hybrid with 
pollen from one of the parents. I conceive that, unless so fertilized, the 
chances are infinitely great against the production of fertile ovules at all. 
In cases where fertile ovules happen to be produced by the self-fertilization 
of hybrid plants, I assume that the pollen engaged in the act of fertilization 
is either normal or so nearly so in structure as to effect fertilization almost 
as perfectly as pollen from one of the parent plants would do; and that 
such normal or nearly normal pollen, as well as a sufficiently perfect stig- 
matic surface, are produced as the result of the tendency, before alluded to, 
to revert to the parental type. 
In fact, I take it to be a law of nature that modifications acquired either 
suddenly or slowly as the results of the operation of external causes, become 
essentially and naturally incorporated into the organism, and will, the con- 
ditions of life remaining the same, be transmitted to the offspring ; whilst it 
is equally a law of nature that the offspring arising from the union of 
organisms generically allied. but specifically distinet, tends to throw off the 
peculiar characteristics derived from the one parent or the other. I con- 
ceive also that unless this tendency to reversion be aided or ministered to 
by impregnating the ovule with perfectly normal pollen from one of 
the parents, the hybrid would rarely produce ovules capable of fertili- 
zation. 
Now, in applying the above views to the case of the New Zealand Veroni- 
cas, I take into consideration the peculiar physical characters of the 
. country. 
The Middle Island contains a mountain district some hundreds of miles 
long by fifty or sixty broad, washed by the sea on three sides, and yet attain- 
ing, on à base of twenty or thirty miles, a summit-level in many parts above 
the limit of perpetual snow. This mountain district is composed of a great 
variety of rocks, and is broken up in a manner probably without precedent 
on the surface of the globe at any similar elevation above sea level. 
For example, the Waiau River, flowing in a valley separated by a chain of 
mountains only five or six miles through from the nearly parallel valley of 
the River Clarence, has for about forty miles of its course a uniformly lower 
level of nearly twelve hundred feet. Besides this difference in altitude, the 
western side of the Waiau Valley is bounded by the Spencer Mountains, 
fully nine thousand feet high, sheltering it from the north-west winds, which 
break with terrific violence over the lower mountain ridge dividing it, on its 
eastern side, from the valley of the Clarence. The climates of these two valleys 
are consequently perfectly dissimilar. The dividing ridge, however, is covered 
5 
