432 



HUTCHINSON'S POPULAE BOTANY 



Photo by] 



FIG. 535. DWABF ORCHIS (Orchis ustulata). 



[E. Step. 



A diminute species of dry pastures and downs. The flowers are only a third of an inch in their longest measurement. 

 The arrangements of the flower are similar to those of the Spotted Orchis. 



any small delicate object by gripping it like a clip " (fig. 506) ; and these 

 clips are so disposed in the flower that when an insect visits it for nectar a 

 foot is pretty sure to get caught by one of them. On trying to free itself 

 the insect brings away the pollinia, which then, by a remarkable twisting of 

 the ligulate strands which connect them with the clip, are brought close 

 together. This facilitates their insertion by the insect in the stigmatic 

 chamber of a new flower, where, by a breaking of the strands, the leg 

 and its burden part company. The clips, however, remain attached to the 

 insect ; and wasps and flies have been caught with as many as eight of 

 these vegetable pincers fastened to a single foot. 



The Brazilian Asclepiad, Araujia albens (Physianthus albens of gardeners) 

 has acquired an evil reputation outside its own country and been nicknamed 

 the " cruel plant," for causes connected with its floral mechanism. In Brazil 

 the cross-pollination of its tubular flowers is effected chiefly by humble-bees, 

 which find no difficulty in pulling themselves free when their feet get caught 

 in the slit-like notches that guard the way to the pollinia; and thus the 

 pollen-masses get carried off to new flowers. In other parts, however, as 

 Michigan, Italy, and the Orange Free State, the plant is visited in large 

 numbers by moths, whose complete ignorance of the mechanism of the 



