PLANT HYBRIDIZATION BEFORE MENDEL 161 



Wiegmann, through forty years of observation, including the 

 fact of having actually produced two geranium crosses as early 

 as his sixteenth year, was already predisposed toward the affirma- 

 tive of the question submitted. His investigations, begun in 1822, 

 were finally published in 1828 (7). In order to overcome all 

 possible criticisms from the opponents of the idea of sexuality in 

 plants, which he considered might be directed against what he 

 designates as "an unnatural handling of plants in pots," he con- 

 ducted his operations in the open ground, in connection with 

 which, he alludes to the several hindrances he was obliged to 

 undergo, "weak sight, a trembling hand, and painful bending and 

 kneeling." (7, p. 2.) 



Wiegmann refers to the main failures encountered, including 

 the attempted repetition of a number of Kolreuter's experiments, 

 as being probably due in part to having attempted crosses be- 

 tween different genera. 



"since many stigmas, according to my numerous experiments, take the 

 pollen of too distant genera either not at all, or with extreme difficulty." 

 (p. 2.) 



"plants which together are to produce hybrids," he says, "must have 

 some relationship with one another, as Kolreuter has already remarked. 

 The nearer the parent plants are related to one another, the more easily 

 will hybrid fertilization succeed ; most easily in the case of different 

 sub-species or varieties ; then different species of the same genus ; less 

 easily in the case of plants of different genera." {ib., p. 26.) 



Wiegmann, however, was entirely free from any rigid dog- 

 matic attitude on the species question. His views in this regard 

 are completely modern. Continuing the above, he says : 



"Yet at the same time, one needs indeed pay less attention to differ- 

 ences based on artificial generic characters. Genera like Pisum and Vicia, 

 Ervum and Vicia, Lychnis and Cucubalus, are in their nature so related 

 that hybrids can arise from them, as Kolreuter and I have demonstrated." 



"So much the more I dispute his opinion," he says of Kolreuter, "re- 

 specting the difference between true 'species' and 'variety' falsely de- 

 rived from the fertility or infertility of the hybrid plants." {ib., p. 25.) 



Wiegmann, in fact, regards chance crossing in nature, between 



species or sorts of plants, as having given rise to new agricultural 



races. 



"It appears from my experiments," he says (p. 26), "that many species, 

 or constant subspecies, e.g., Pisum arvense, Vicia leucosperma, Vicia faba 

 (red-seeded), as well as the most of the varieties of cabbage and the 

 cereals, whose origin is unknown, possibly are hybrid plants, which 



