"W. Tbaveks. — Hyhridization of Plants. 83 



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 froin. the union of 

 organisms generically allied but specifically distinct, 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 a base of t\\'enty 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. 

 Eor example, the "Waiau Eiver, flowing in a valley separated by a chain of 

 mountains only five or six miles through from the nearly parallel valley of 

 the Eiver 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 



