Roberts: The Founders of the Art of Breeding 



259 



cotyledons, can be crossed . . . (p. 

 14) . The facility of making a first cross, 

 between any two species is not always 

 governed by their systematic affinity or 

 degree of resemblance to each other. 

 This latter statement is clearly proved 

 by the difference in the result of reci- 

 procal crosses between the same two 

 species, for according as the one species 

 or the other is used as the father or the 

 mother, there is generally some differ- 

 ence, and occasionally the widest pos- 

 sible difference, in the facility of effect- 

 ing an union. The hybrids, moreover, 

 produced from reciprocal crosses often 

 differ in fertility" (p. 16). 



Again he says: "There is often the 

 widest possible difference in the facility 

 of making reciprocal crosses. Such 

 cases are highly important, for they 

 prove that the capacity in any two 

 species to cross is often completely inde- 

 pendent of their systematic affinity, 

 that is, of any difference in their struc- 

 ture or constitution, excepting in their 

 reproductive systems (p. 14). It can 

 thus be shown that neither sterility nor 

 fertility affords any certain distinction 

 between species and varieties. The 

 evidence from this source graduates 

 away, and is doubtful in the same 

 degree as is the evidence derived from 

 other constitutional and structural 

 differences" (p. 4). 



Darwin finally summarizes the evi- 

 dence as follows: "First crosses between 

 forms, sufficiently distinct to be marked 

 as species, and their hybrids, are very 

 generally, but not universally sterile. 

 The sterility is of all degrees and is often 

 so slight that the most careful experi- 

 mentalists have arrived at diametrically 

 opposite conclusions in ranking forms by 

 this test" (p. 44). 



hi 1861 the Paris Academy of the 

 Sciences proposed the following problem 

 to receive the grand prize in the physical 

 sciences: "To study plant hybrids from 

 the point of view of their fecundity, and 

 of the perpetuity or non-perpetuity of 

 their characters. "The production of 

 hybrids among plants of different species 

 of the same genus is a fact determined a 

 long time since, but many precise re- 

 searches still remain to be made in 



order to solve the following questions, 

 which have an interest equally from the 

 point of view of general physiology, and 

 of the determination of the limits of 

 species, of the extent of their variations. 



"1. In what cases of hybrids are they 

 self-fertile ? Does this fecundity of 

 hybrids stand in relation to the external 

 resemblances of the species from which 

 they come, or does it testify to a special 

 affinity from the point of view of 

 fertilization, as has been remarked 

 regarding the ease of production of the 

 hybrids themselves ? 



"2. Do self-sterile hybrids always owe 

 their stability to the imperfection of the 

 pollen ? Are the pistil and the ovules 

 always susceptible of being fecundated 

 by a foreign pollen, properly selected ? 

 Is an appreciable imperfect condition 

 sometimes observed in the pistil and the 

 ovules ? 



"3. Do hybrids which reproduce 

 themselves by their own fecundation 

 sometimes preserve invariable characters 

 for several generations, and are they 

 able to become the type of constant 

 races, or do they always return, on the 

 contrary, to the forms of their ancestors 

 after several generations, as recent 

 observations seem to indicate ? 



THE IDEAS OF GODRON 



The two chief competitors under the 

 Academy's offer were Charles Naudin 

 of the Museum of Natural History at 

 Paris, and D. A. Godron of the Uni- 

 versity at Nancy, the prize being 

 awarded to the former. The papers of 

 both appeared in Vol. 19 of the Annales 

 des Sciences Naturelles (Botanique), 4 

 me. Serie (1863). 



The title of Godron 's thesis was 

 "Des hybrides vegetaux, consider ees au 

 point de vue de leur fecondite et de la 

 perpetnite ou non-perpetuite de leurs 

 characteres.'' His paper is chiefly de- 

 voted to the solution of the question as 

 to whether "hybrids reproducing by 

 self-fertilization sometimes keep their 

 characters invariable during several 

 generations, and whether they are able 

 to become the types of constant races, 

 or whether, on the contrary, they always 

 return to the forms of one of their 



