THE WATSONIA 85 



color the extreme abundance of white flowers is 

 sufficiently accounted for. 



It is true that flowers that bloom in the 

 shadow, and particularly those that open in the 

 twilight or at night, are almost universally white 

 also, but this is sufficiently explained by natural 

 selection, since white flowers are more conspicu- 

 ous at night than those of any other color. 

 Moreover, it must be recalled that white objects 

 transmit heat less readily than dark ones, so 

 white is not a bad color for a night-blooming 

 flower, inasmuch as it conserves the internal 

 heat even if it is not called upon to shut out 

 heat from the sun's rays. 



THE SEQUENCE OF COLOR DEVELOPMENT 



All this is more or less axiomatic, but the fur- 

 ther development of the theory of flower colora- 

 tion involves a certain amount of assumption, 

 and must be held only as a tentative theory. 



Briefly stated, the essentials of the theory are 

 that the original or earliest color of the flower 

 was green in imitation of the leaf. All the 

 older or primeval types of plants cycads, pines, 

 cypress, ferns, etc. have green flowers or sub- 

 stitutes for them even to this day; in some cases 

 slightly tinged with yellow. It is suggested that 

 the color next developed was blue, the genesis of 



