Roberts: The Founders of the Art of Breeding 



269 



Two observations of Gartner's were 

 verified by Wichura — the identity of 

 reciprocal crosses (pp. 51 and 186), and 

 thefact of "variation" in hybrid progeny. 



The question was as to the relative 

 importance of the egg or the pollen in 

 the result of fertilization. Wichura 

 says (p. 57): "One sees the question is 

 still far removed from having been 

 brought to light, but from Gartner's 

 and my own observations it appears at 

 least determined that the products of 

 hybrid pollen in breeding are more 

 various than those of the pollen of true 

 species." 



From the generally admitted identity 

 of reciprocal crosses, Wichura draws the 

 following conclusion (p. 86): "We 

 have found that the products which 

 come from reciprocal crossing, unlike 

 the well-known experiments made in 

 the animal kingdom, completely coin- 

 cide with each other. From this it fol- 

 lows, however, with mathematical necessity, 

 that the pollen cell must have exactly the 

 same share in the conformation of the 

 fertilization product as the egg.'' (Italics 

 inserted.) 



vSo far as the writer knows, this is the 

 first complete categorical statement in 

 the literature of breeding* of such a 

 conclusion as to the behavior of the sex 

 cells in amphimixis. One is completely 

 impressed, in reading Wichura 's work, 

 with the scrupulous care, accuracy and 

 precision with which his hybridization 

 experiments were carried out. One or 

 two passages in point are interesting. 

 Referring to a case of Gartner's, where 

 exceptional types appeared in the midst 

 of "a greater number of hybrid plants of 

 completely similar hybrid types," he 

 says (p. 53): "To judge concerning the 

 here-mentioned exceptional types with- 

 out myself having seen them is scarcely 

 possible. From the relatively limited 

 number of my experiments, which have 

 not yielded the like, I cannot, to be 

 sure, deny its possibility, but here like- 

 wise, as above in the case of reversions, 

 the suspicion of a complete disturbance 

 of the experiment, whether that the 

 protection had not been complete, or the 

 pollen utilized for fertilization not pure, 

 or the seeds sown not free from foreign 



admixture. Whoever knows from his 

 own experience how much care must be 

 observed in order to keep an experiment 

 clean becomes skeptical respecting all 

 results of an experiment which vary 

 from the usual rule, of the correctness of 

 which one has not achieved conviction 

 through his own observation." 



Regarding these and other so-called 

 anomalies as the result of crossing, he 

 again says (p. 89) : "That concerning all 

 these points and many other disputable 

 questions . . • . we know so little, has 

 indeed its basis in part in the method 

 hitherto of artificial cross-fertilization, 

 which suffers from the double deficiency 

 that the care requisite to the correctness 

 of the experiment, through the exclusion 

 of foreign pollen, has not been taken in 

 the first place, and second, that although 

 many experiments have been instituted 

 in very different families, nevertheless 

 the individual hybrids have not been 

 bred and observed in sufficient number. 

 However, this is imperative throughout 

 for attainment of general results. Only 

 when one has at hand the same hybrid 

 in hundreds of cases, partly from the 

 same, partly from different parents, 

 repeated through different years, only 

 then will one be in position to separate 

 the essential phenomena of hybridiza- 

 tion from the more accidental ones." 



Finally (p. 92), Wichura remarks, 

 expressing the hope that a learned 

 society or an individual with means 

 might repeat his own experiments on a 

 larger scale: "The most scrupulous 

 exactness in such case would be indis- 

 pensable. Failing this, and especially if 

 the possibility of the access of foreign 

 pollen is not completely excluded, then 

 all experiments, the more extensively 

 they are undertaken, only contribute 

 so much the more to the confusion of 

 the matter. This must be taken to 

 heart." 



Regarding the possibility of securing, 

 in any given case, a cross, Wichura 

 remarks (p. 84): ". . . only such 

 species can be united in a hybrid which 

 agree in relatively many characters, and 

 correspondingly in many life conditions. 

 Experience teaches the same thing in the 

 familiar rule, that hvbrid combinations 



