BOTANY 165 



method involved the formulation of some general notion, then 

 the search for facts that agreed with it. The effect of eman- 

 cipation from this method finds a typical illustration in the 

 history of the establishment of the fact of sexuality in plants. 

 In 1583 Caesalpino argued from the nature of the plant 

 against the existence of sexuality, while Linnaeus, by a simi- 

 lar application of Aristotelian logic, argued in favor of sex- 

 uality. Csesalpino reasoned thus: The vital principle of the 

 plant resides in the pith, hence seeds must originate from the 

 pith; therefore sexuality is contrary to the nature of plants. 

 Linnaeus started with the dictum, stated by Harvey, "Omne 

 vivum ex ovo." Plants are alive, argued Linnaeus, therefore 

 they must come from eggs. Hence sexuality follows from 

 the nature of plants. This teetering of probabilities con- 

 tinued for over one hundred years, until about 1694, when 

 Rudolph Jacob Camerarius had his attention arrested by the 

 fact that a pistillate mulberry tree, growing quite apart from 

 any staminate trees, bore fruit that contained only undevel- 

 oped seeds. From this observation as a starting point, he 

 began to make experiments on other dioecious plants, as a 

 result of which he adduced abundant evidence that plants 

 have sex. The proof was conclusive, but the botanical world, 

 unable to overcome the inertia of Aristotelian methods of 

 reasoning, was unable to distinguish the positive evidence 

 of Camerarius from the a priori statements of others. Aris- 

 totelian method found a later expression in the so-called na- 

 ture-philosophy, which had little respect for facts and evi- 

 dence, and so the debate on this question dragged on through 

 another hundred years. Then, in 1849, Karl Friedrich Gart- 

 ner published his "Versuche und Beobachtungen ilber die 

 Befruchtung durch den eigenen Pollen". Note the title of 

 this book, "Versuche und Beobachtungen" (Experiments and 

 Observations). There lies the secret of its power as a work 

 of science. The times were now ripe, and the question of 

 the sexuality of plants, which otherwise might still be a suit- 



