230 



THE FLOWER. 



under side of the abdomen frequently touching the stigma, while 

 the proboscis is searching round the bottom of the flower, liberat- 

 ing the stamens in the process, which one by one project their 

 pollen upon the under side of the insect's body. In the passage 

 from flower to flower, pollen is thus conveyed from the anthers 

 of one to the stigma of another. 



420. Iris has three stamens, one before each sepal or outer 

 lobe of the perianth, and behind each petal-like lobe of the style 



(Fig. 459) : the stigma, a 

 shelf-like plate of each lobe, 

 is just above the anther ; 

 but, as the anther faces 

 outward and the stigma is 

 higher and faces inward, no 

 pollen can find its way from 

 the one to the other. But the 

 adaptation of parts is admir- 

 able for conveyance by bees, 

 which, standing upon the 

 only landing place, the re- 

 curved sepal, thrust the head 

 down below the anther, and 

 in raising it carry off pollen, 

 to be afterwards lodged 

 upon the stigmas of other 

 flowers which they visit. 



421. Transportation of Pollinia, or of all the pollen in a 

 mass, is effected in most of the species of two large orders, 

 not otherwise allied, the Asclepiadacese and the Orchidacese. 

 While in the Iris family the number of stamens is reduced from 

 six to three, in all the Orchis family, except Cypripedium, the 

 stamens are further reduced to a single one ; but the pollen is 

 peculiarly economized. That of Arethusa is in four loose and 

 soft pellets, in an inverted casque-shaped case, hinged at the 

 back, resting on a shelf, the lower face of which is glutinous 

 stigma, over the front edge of which the casque-shaped anther 

 slightly projects ; and this anther is raised by the head of a bee 

 when escaping out of the gorge of the flower. The loose pellets 

 of pollen are caught upon the bee's head, to the rough sur- 

 face of which they are liable to adhere lightly and so to be carried 

 to the flower of another individual, there left upon its glutinous 



FIG. 469. Flower of Iris pumila, with front portion and half of one petaloid style- 

 lobe and stigma cut away. The section of the stigma is seen edgewise: the rough 

 upper surface only is stigmatic. 



