PLANT HYBRIDIZATION BEFORE MENDEL 39 



in which each of the five separate stigmas is directed outward 

 toward its own cell of the ovary. Kolreuter made rather extensive 

 examinations of the pollen grains of several hundred genera, and 

 comments on their form and relative sizes. He remarks on the 

 fact that, in almost all grasses, the stigmas are self-pollinated 

 within the closed flower. He comments at some considerable 

 length upon the manner of pollination of a number of species, 

 and especially upon the fact of pollination by insects. Regard- 

 ing the activity of insects in fertilization, the only example thus 

 far known, he says, is the fig tree : 



"is it then," he continues (p. 19), "something so wholly exceptional, if 

 Nature, for the maintenance of certain creatures, makes use of others 

 which have no resemblance with them. Experience has taught me pre- 

 cisely the truth of this, that has long been maintained for the fig tree, 

 and for the case of many other and in part very common plants. In all 

 the Cucurbitaceae, in all the Iridaceae, and with not a few plants from 

 the order of Mallows (Malvaceae), fertilization of the female flowers 

 and stigmas occurs only through insects." 



In speaking of the fact that cucumbers and melons, confined 

 within hot-beds, do not set fruit, he says : 



"Up to the present day one has ascribed to the wind the pollination of 

 the female flowers ; but one would necessarily have had to come to 

 other ideas, if one had only brought the location of the male and fe- 

 male flowers, their form, and the structure of the pollen into closer 

 observation." (p. 20.) 



He then continues : 



"And how can one do this, without immediately finding the cause of 

 the pollination in those busy creatures (i.e., the insects). Certainly, any 

 other one, who before me had instituted these observations, would have 

 long since discerned them, and have drawn aside the curtain of this se- 

 cret of Nature for himself and all investigators of Nature." (p. 20.) 



Kolreuter investigated the pollination of the Iris (pp. 22-4), 

 and describes with scientific and minute exactness the details of 

 his discoveries. He was apparently the first to discern the actual 

 location of the stigmatic surfaces, in the triangular area toward 

 the apices of the leaf-like so-called stigmas, the inner surfaces of 

 which he found to be covered "over and over with pointed papil- 

 lae" smeared with a moist secretion. 



"I did not let the matter rest there," he says, "but instituted very many 

 experiments thereupon, which finally completely convinced me that this 

 small part is the true stigma in these plants." (p. 23.) 



The opening of the flower, and the relations of the several 



