PLANT HYBRIDIZATION BEFORE MENDEL 51 



(p. 140.) In the spring of 1763 the experiment was repeated with 

 a few other plants. When the stigmas of Nicotiana rustica showed 

 here and there drops of the secretion, he spread almond oil over 

 the surface with a fine brush, mixing it with the stigmatic secre- 

 tion, and spreading the whole over the entire surface, then apply- 

 ing a more than sufficient quantity of pollen. Pollination took 

 place successfully. Upon four other flowers, he used hazel-nut oil, 

 upon two, oil of jasmine, and upon four, linseed oil, with the 

 same result. With "distilled or artificial oils" no fertilization took 

 place, as also with animal fats and oils. The use of oil of both 

 sweet and bitter almonds, in the case of Verbascum blattaria, re- 

 sulted in fertilization. With pumpkins, however, the experiment 

 failed, although, as he says: "the oil of almond had penetrated 

 the ovary to over its half." (p. 142.) Kolreuter concludes, on 

 the basis of these experiments, that the essential fertilizing ma- 

 terial, issuing from the pollen grain, is the homogeneous fluid 

 oily substance, and not the granular material. The fact that this 

 portion of the pollen material, in his opinion, mingled freely with 

 the added vegetable oils, and still penetrated to the ovary, fertil- 

 ization following, was evidence, in his view, that both the fluid 

 portion of the pollen exudate and the stigmatic secretion were 

 alike oily substances, mixing freely with other oils of a vegetable 

 nature. Kol renter's assumption of an exudation under pressure 

 from the pollen grains of their contents lay of course at the basis 

 of this conclusion. He knew nothing of the growth of the pollen 

 tube, the character of which precluded any admixture of the con- 

 tents of the pollen grains with the stigmatic secretion or anything 

 else. However, considering the lack of morphological knowledge, 

 Kol renter's experiment may well be regarded as in every sense 

 scientific in spirit, and in the manner in which the conclusions 

 were drawn. 



Of the eight experiments in crossing species of Dianthus, three 

 were species or variety-crosses, three were back-crosses upon F^ 

 hybrids, one a self-fertilized Fj, and one a compound cross. From 

 the variations in type obtained in two back-crosses — (Dianthus 

 chinensis X carthusianoruni), and (Z). chinensis X carthusia- 

 noruin) X carthusianorum, — Kolreuter concludes that: 



"The union of the fertilizing materials in the production of hybrids 

 in the first descending or ascending degree does not take place by far 



