PLANT HYBRIDIZATION BEFORE MENDEL 147 



kept clearly in mind that, from his point of view, a plant was 

 a constant struggle between two opposing forces, the force exerted 

 by its immediate parentage and that exerted by its ancestry. 



"The characters of an individual plant are the result of the action of 

 two distinct, and in a certain measure, opposed forces. The first repre- 

 sents the tendency to individual variation or idiosyncrasy. It causes the 

 individual to present characters different from those of its ancestors, 

 while remaining enclosed within the limits assigned to the species. This 

 force, although probably complex in its nature as in its effects, may, 

 for facility of reasoning, be considered as 'simple.' The other force is 

 that which calls upon the individual to reproduce the character of its 

 ascendants." (7b, p. 41 ; 8, pp. 33-4.) 



"This latter, simple, and insofar as the ancestors are concerned, of 

 the individuals which one considers have presented invariable charac- 

 ters, becomes on the contrary evidently complex, if there have already 

 been some variations. The tendency to assemble a collection of beings 

 dissimilar among themselves cannot be the effect of a single force, but 

 the resultant of several more or less divergent forces. One may call 

 'atavism' the tendency which, in this case, calls the plant to resemble 

 the totality of ascendants, and 'heredity' that which leads it to reproduce 

 the characters of the individual from which it immediately descends." 

 (7b, p. 4.) 



In another place (yd), Henry de Vilmorin quotes his father's 

 viewpoint again as follows : 



"if we consider a seed at the mornent when, put into the ground, it 

 gives birth to a new individual, we may regard it as solicited, so far as 

 the characters are concerned which the plant must exhibit to which it 

 is to give birth, by two distinct and opposing forces. These two forces, 

 which act oppositely, and from the equilibrium of which results the 

 fixity of species, may be considered as follows : 



"The first, or centripetal force, is the result of the law of the re- 

 semblance of children to fathers, or atavism. Its operation has for its 

 results the maintaining, within the limits of variation assigned to the 

 species, of the departures produced by the opposite force. 



"The other is the centrifugal force, resultant of the law of differences 

 in individuals or idiosyncrasy, and causes each one of the individuals 

 composing a species, whether one is able to consider it as the progeny 

 of a single individual or of a pair, to present differences which consti- 

 tute its own physiognomy, and produce that infinite variety in unity 

 which characterizes the works of the Creator." (p. 489.) 



Vilmorin thought that the action, of these diverse tendencies 

 would be measured by the proportion of plants with blue flowers, 

 and of plants with rose-colored flowers, respectively, which pro- 

 ceed from the seeds of an individual of one of these two colors, 

 and especially since, in his view, there were no intermediates. The 

 inferences, rather than conclusions, which Vilmorin believes he is 

 able to derive from the experiment, are based upon the fact that 



