454 



REPRODUCTION. 



1 1 70. The colors of flowers have been variously classified ; thus 

 De Candolle divides them into a xanthic (3 - ellow) and a cyanic 

 (blue) series, both of which can pass into red and white. With 

 few exceptions, these two series are not represented in the same 

 blossom. 



1171. The odors of flowers depend in some cases (e. g. 

 orange-blossoms) upon the presence of a volatile oil which can 

 be extracted by distillation ; but in many other instances the 

 odoriferous principle cannot be separated by chemical or other 

 means. 



1172. White flowers are more generally fragrant than those 

 of any other color. ' ; The fact of a larger proportion of white 

 flowers smelling sweetly may depend in part on those which are 

 fertilized by moths, requiring the double aid of couspicuousness 

 in the dusk and of odor. So great is the economy of nature that 

 most flowers which are fertilized by crepuscular or nocturnal 

 insects emit their odor chiefly or exclusively in the evening." 1 



1 Darwin: The Effects of Cross and Self Fertilization in the Vegetable 

 Kingdom, 1876, p. 374. 



According to Kohler and Schiibeler (cited by Balfour), the distribution of 

 odor with regard to color is as follows : 



The following classification, taken partly from Trinchinetti, as cited by 

 Balfour, indicates the diversity which exists in regard to the periods and per- 

 manence of odors of flowers. 



(1) Flowers which are odoriferous at the time of opening and which remain 

 so throughout ; c. g. most Roses. 



(2) Flowers in which the intermission of odor is connected with their 

 opening and closing ; and in this class there are two subdivisions : 



(a) Those which are closed and scentless during the day, and are open and 

 odoriferous at niglit. ; e. g. Mirabilis Jalapa, Cereus grandiflorus, etc. 



(b) Those which are closed and scentless at night, and are open and odor- 

 iferous during the day ; e. g. Convolvulus arvensis, Cucurbita Pepo, some 

 species of Nymphaea. 



