Darwin on the Effects of Cross- and Self- Fertilization. 133 



America) ; and this is all concerning the United States. Can 

 it be that there are no references in print to the most familiar 

 fact that our humming-bird is very fond of sucking the blos- 

 soms of Trumpet Creeper (Tecoma radicans) and of Honey- 

 suckles? Both these are, in size and arrangement of parts, well 

 adapted to be thus cross-fertilized. 



Flowers are rendered conspicuous to birds and still more to 

 insects, by bright colors. And as "almost every fruit which 

 is devoured by birds presents a strong contrast in color with 

 the green foliage, in order that it may be seen, and its seeds 



I," so the proportional 

 colors of the corolla, or in some i 

 of adjoining parts of the flower, or 

 related to visiting insects. — have come to pass, as Darwin would 

 say, in consequence of the \ isits of insects, through the advan- 

 tages in vigor and productiveness 



He is ready to adopt even the idea of Conrad Sprengel, which 

 seemed to be so fanciful, that marks and streaks on the corolla 

 serve as guides to the nectary : for, although insects are well 

 able to discover the nectar without the aid of guiding marks, 

 yet they are of service by facilitating the search and enabling 

 insects "to suck a greater number of blossoms within a given 

 time, which is tantamount to greater opportunity for cross-fer- 

 tilization. 



That odors attract insects is certain and many flowers are 

 both conspicuous and odoriferous, while others make up in 

 fragrance what they lack in show. " Nageli affixed art 1 * 5 ™ 1 

 flowers to branches, scenting some with essential oils 

 leaving others unscented; and insects were attracted 1 

 former in an unmistakable manner." 



" Of all colors white is the prevailing 

 a consider: <n smell 



color, namely, 14-6 per cent; of red, only 8 



erous. The fact of a larger proportion of '*««■> -- 



sweetly may depend in part on those which are fertilized by 



moths requiring the double aid of eonspicuousness in the dusk 



and of odor. So great is the economy of nature, that most flowers 



which are fi liar or nocturnal insects a 



odor chiefly or exclusively in the evening. Some flov. 



ever, which raw depend solely on this quality 



for their fert night-flowering stock (Hespens) 



and some species of Daphne; and these pres 



flowers which are fertilized by insects being obscurely colored 



" The shape of the 1 1 ■*■ "J "Jf" 



wise related to the particular ki 



visit the flowers; this has been well shown by H. Mailer bv his 

 comparison of lowland species, which are chiefly visited by bees, 

 with Alpine species belonging to the same genera, which are 

 visited by butterflies." 





