INTRODUCTION. 



xxvii 



garden specimens are often tinged with, pink, 

 and still more frequently double : these characters 

 being either unimportant or inconstant,— for blue 



DOG-VIOLET, SCENTED VIOLET. 



flowers generally have a great tendency to sport 

 to white, and double flowers are not perpetuated 

 by seed, — the blue, white, pink, and double sweet 

 violets are not considered distinct species, but 

 mere varieties. Now there are many plants which 

 bear a close resemblance to a violet in the struc- 



