COLOR IN PLANTS 157 



that the bee in entering the flower to reach the nectar 

 will press its head against the rostellum (5). When the 

 bee withdraws, the rostellum, with its two pollen masses, 

 sticks to its forehead (6), and the pollen masses are thus 

 carried to the next blossom visited. At first the pollen 

 masses stand erect upon the forehead of the bee (5 and 6), 

 but, as the bee flies through the air, the stalks of the pollen 

 masses dry slightly and bend downward (7), so that, when 

 the bee enters another flower, the pollen masses are pressed 

 against the stigma. Thus cross-fertilization must be fre- 

 quently effected, the bees carrying the pollen not only from 

 blossom to blossom of the same plant, but also from one 

 plant to another. 



The flowers of Salvia have adopted another and equally 

 interesting method of reaching the same result. In these 

 blossoms the stamens are hinged, and the lower end of the 

 stamen, below the hinge, is so placed that a bee, in entering 

 the blossom, will push against it, and in doing so will cause 

 the other end of the stamen with its pollen to drop down and 

 dust the back of the bee with pollen (Plate 89, B, /, j, ./, and 

 5). This pollen will be carried to the next flower visited by 

 the bee. Frequent cross-fertilization is secured by another 

 simple character of these blossoms. The pollen is mature by 

 the time the blossom bud opens, but at this time the pistil is 

 short and lies arched in the upper part of the blossom (/). 

 As the flower grows older, the pistil elongates and bends 

 downward, so as now to come into contact with any insect 

 which may visit the flower with its load of pollen, thus secur- 

 ing fertilization (2). As the pollen and the pistil are not 

 ready for fertilization at the same time, no blossom will be 

 self-fertilized ; and, as the insects pass frequently from plant 



