24 INTRODUCTION. 



marked the transitions of one colour to another. 

 He says, — 



" The colours of flowers are variable, but only 

 within certain limits. Lively yellow are the 

 least variable ; dull yellow in general become 

 white or red, but never blue ;" and adds, that it 

 is not likely we shall ever see a blue Dahlia. 



In proportion as plants are cultivated, and 

 undergo the constant and various manipulations 

 of the florist, so are they changed in habit and 

 colour. Bulbs, as being of all others most easily 

 transported, and yielding readily their fine con- 

 spicuous flowers, have always had an extra share 

 of the care and regard of mankind. Placed in 

 closely planted order in the garden, they imparted 

 and received all the chances and influence of 

 cross impregnation by accident. As favourites, 

 they had always the best and richest composts to 

 invigorate and encourage them, and in which 

 various qualities existed that would change their 

 natural hues, or add to the brilliancy of their 

 original colours. These circumstances suffi- 



