138 PLANT HYBRIDIZATION BEFORE MENDEL 



leaves colored white, yellow, red, or brown; in the arrangement 

 of the leaves, as in the sudden appearance, on an ordinary alter- 

 nate-leaved plant of Rosa alba, of a shoot with opposite leaves, 

 propagated as Rosa cannabifolia. From the evidence he concludes 

 that cultivation sets up within the plant a condition of instability, 

 which gives rise not only to seed variation, but to variation within 

 the plant itself — what we would call bud-variation or "somatic 

 segregation," as in the case just cited; the case of a chrysanthe- 

 mum reported, which bore at the same time yellow- and rose- 

 colored flowers; and of a citrus fruit half-and-half orange and 

 lemon. Another case cited by Verlot is that of a variegated 

 Camellia imperialis, which for twelve years had constantly given 

 brilliant white flowers set off with rose-colored striations and 

 variegations, and upon which a small branch appeared one year, 

 bearing three flowers in a group, of a uniform color, the same 

 tint as that of the striations and variegations of the other flowers. 



"It is evident in these cases," says Verlot, "that the colorations dis- 

 join, and that this variation returns by disjunction to its colored parent 

 for certain plants of hybrid origin." (6, p. 67.) 



"As we see," he says, "by the sole fact that a plant is cultivated it is 

 forced to vary. The instability of a cultivated plant is even evident in 

 certain cases, in such a way that it does not only manifest itself in the 

 direct descendants of the plant, but also in the plant itself. Thus, while 

 the generality of the branches of a plant bear leaves, flowers and fruits 

 of definite forms or colors, a branch is sometimes produced, in which 

 the leaves, flowers, and fruits present completely different characters. 



"We recognize that culture has been, and is still, the essential cause 

 of the variation of plants, and that thereby man has, so to speak, com- 

 pelled them to re-clothe themselves with new forms appropriate to his 

 needs or to his caprices." (6, p. 5.) 



The above statement excellently presents the older point of 

 view regarding variation. Such cases as the rose, chrysanthemum 

 and orange, and the famous chimaera, Cytisus adami (C. pur- 

 pureus X Laburnum), Verlot accounts for under the guise of 

 Naudin's conception of "disjunction." 



"It Is by disjunction that, in these last cases, the specific forms thus 

 appear in hybrid plants, and it is with woody plants, it will be noticed, 

 that this fact achieves all the phases of existence of a hybrid plant, an 

 existence of which this disjunction would be the last term." (6, p. 14.) 



He then refers to Naudin's case of disjunction in Datura, which 

 is elsewhere discussed. 



Verlot's expression of view on the matter of methods of selec- 



