84 GENETICS AND EUGENICS 



of the general behaviour of hybrid plants, which was scarcely bettered until 

 Mendel made his observations a century afterwards. 



Kolreuter found thai the hybrid offspring of two diflferent plants gener- 

 ally took as closely after the plant which yielded the pollen as after that 

 upon which the actual hybrid seed was borne. Indeed, he found that it 

 made little or no difference in the appearance of the hybrid which of the 

 parental species was the pollen-parent (male), and which the seed-parent 

 (female) — that is to say, in the case of plants the result of reciprocal 

 crosses is usually identical. Thus, for the first time it was definitely shown 

 that the poUen-grain plays just as important a part in determining the 

 characters of the offspring as does the ovule which the pollen-grain fer- 

 tilizes. This was a wholly novel idea in Kolreuter 's time, and the fact was 

 scarcely credited by his contemporaries. 



Kolreuter had no means of discovering that the contents of a single 

 pollen-grain unite with the contents of a single ovule in ferlilization. But 

 he ascertained by experiments that more than thirty seeds might be made 

 to ripen by the application of between fifty and sixty pollen-grains to the 

 stigma of a particular flower, so that, if he had had any hint of the actual 

 microscopic processes of fertilization, he would have been quite prepared 

 for the more fundamental discovery. 



Kolreuter, indeed, believed that the act of fertilization consisted in the 

 intimate mingling together of two fluids, the one contained in the pollen- 

 grain, and the other secreted by the stigma of the plant. The mingled 

 fluids, he supposed, next passed down the style into the ovary of the plant, 

 and arriving at the unripe ovules, initiated in them those processes which 

 led to the formation of seeds. In this belief Kolreuter simply followed the 

 animal physiologists of liis time, who looked upon the process of fertiliza- 

 tion in animals as taking place by a similar mingling of two fluids. Now 

 that we know that fertilization consists essentially in the intimate union 

 of the nuclei of two cells, one of which, in the case of plants, is the ovum 

 contained within the ovule, whilst the other is represented by one of a 

 few cells into which the contents of the pollen-grain divide, we can under- 

 stand more clearly the bearing of Kolreuter's observation. And it is 

 greatly to this eminent naturalist's credit that he succeeded in carrying 

 out his observations with so much accuracy, when the full meaning of 

 those observations was of necessity liidden from his comprehension. 



Kolreuter was the first to observe accurately the different ways in which 

 pollen can be naturally conveyed to the stigma of a flower. This may 

 take place either by the pollen-grains falling directly upon the stigma, or 

 by the agency of the wind,, or, lastly, the pollen may be carried by insects 

 visiting the flowers. And he recognized many features characteristic of 

 flowers apt to be fertilized in one or other of these ways in particular. 

 Thus he was aware, for example, of the nature and use of the nectar which 

 so many flowers produce — namely, that it is the substance from which 

 the bees — by far the most diligent visitors of flowers — obtain their 

 honey. 



Curiously enough, Kolreuter was not aware of the existence of any 

 natural wild hybrid plants. But he was quite right in contending that 



