60 EXPERIMENTAL EVOLUTION LECT. 



where all, in a more or less marked degree, at the 

 same time became variegated. This fact, with others 

 which might be quoted, goes to show that variegations 

 depend on some environmental influence. 



Colour variations may, however, be noticed in cases 

 where no environmental influence can, as yet, be 

 traced. Every one has seen cases where the same 

 rose-bush yields flowers of dissimilar colours. Carriere 

 and Andre, 1 to take an instance among many, have 

 noticed a rose of the Mabel Morison variety carrying- 

 white flowers and one single pink one. The branch 

 bearing the pink flower has been grafted on another 

 bush, and it has maintained its special character, 

 yielding always pink roses. Such cases are not of 

 rare occurrence. But how can we understand the 

 cause of this variation ? Environmental influence 

 seems out of the question, and we are at a loss to 

 account for this important variation. 



Similar colour variations are often noticed in fruits, 

 and have often been recorded in connection with 

 grapes. Carriere has quoted a case of this sort, and 

 given a good coloured plate showing well how things 

 stand. In the same bunch of grapes some are black 

 or red, some colourless, and many variegated in 

 different manners. It may seem that these cases are 



3 C<zs dc Dichroisme dans la Floraison tfun Rosier. Rev. Horticole, 

 1888, p. 74. 



