456 



THE ANIMALS AND MAN 



acquired from a previous visit to another flower. Mis- 

 cellaneous small insects alighting on the keel are not heavy 

 enough to depress it, and thus are prevented from entering 

 and stealing the nectar. In the salvias (sages) the corolla 

 is similarly tubular below and two-lipped above, the lower 

 lip serving as an alighting-platform for the insect visitors 

 (usually bees), while the arched upper lip covers and pro- 

 tects the stamens and pistil. 



In the scarlet sage (Salvia sp.) 

 cross-pollination is accomplished by 

 humming birds, which, hovering in 

 front of the narrow mouth of the 

 flower-cup, thrust deeply into it their 

 long bills in the search for small 

 insects which may have entered for 

 nectar. Other flowers regularly visit- 

 ed and cross-pollinated by humming 

 birds are the scarlet currant, various 

 painted cups (Castilleias), the scarlet 

 mimulus, the wild columbine, the 

 trumpet-creeper, the spotted touch- 



\\ 



FIG. 236. Honeybee at me-not, the cardinal-flowers, cannas, 



Asclepias flowers, with legs and fuchsias> Red seems t be ^ 

 still fast in a stigmatic 



chamber of the flower attractive color for humming birds. 



last visited. (Natural A wonderful arrangement to insure 



size; after Stevens.) C ross-pollination by insects is that 

 shown by the milkweeds of the genus Asclepias. Stevens 

 has described this so well ("Introduction to Botany," 

 p. 191 et seq.) that I simply quote here most of his account. 



"As shown in fig. 236, the sepals and petals are reflexed; 

 the stamens are joined throughout their length, and are 

 united to a thick and flat structure at their apices, known 

 as the stigmatic disk, which is also united with the top of 

 the two pistils. The pistils are entirely enclosed by the 

 stamens and the stigmatic disk. Five spreading, hollow 



