Page:History of botany (Sachs; Garnsey).djvu/417

] Geoffrey contributed nothing either to the establishment of the fact of sexuality in plants, or to the decision of the question how the pollen effects fertilisation in the ovule. Nevertheless I have mentioned these two men immediately after those who really developed the sexual theory, because they at least took their stand on experience, and endeavoured, though unsuccessfully, to demonstrate conditions of organisation which should explain the process of fertilisation. We come now to the names of men Leibnitz, Burckhard, Vaillant, Linnaeus who are usually supposed to have aided in establishing the sexual theory, but who may be proved to have contributed nothing whatever to the scientific demonstration of that doctrine. First as regards the philosopher Leibnitz; he says in a letter of 1701, from which Jessen has quoted the most important parts in his 'Botanik der Gegenwart und Vorzeit,' 1864, p. 287: 'Flowers are closely connected with the propagation of plants, and to discover distinctions in the mode of propagation (principiis generationis) is very useful,' etc.; again, 'A new and extremely important point of comparison will be hereafter supplied by the new investigations into the double sex in plants,' alluding, according to Jessen, to those of Camerarius and Burckhard. We shall not expect to find that Leibnitz made experiments himself, and the words quoted merely indicate that he wished to see the parts of the flower employed for purposes of classification, because according to the observations of others they are the instruments of propagation. The remark applies in a still higher degree to Burckhard, who in his letter to Leibnitz of 1702, quoted above on p. 83, further developed the idea intimated by Leibnitz, for he too accepted the sexuality of plants as an established and self-evident truth. The address with which Sebastian Vaillant opened his lectures at the Royal Gardens in Paris in 1717 has often been noticed by the historians of botany. De Candolle, who assigns to him an important share in developing the sexual theory,