CHAP, i.] Adherents and Opponents of Sexuality. 397 



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. Neverthe- 

 less 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, Lmnaeus- 

 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 com- 

 parison 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, 



