Minnesota Plant Life. 



365 



Each milkweed flower consists of a five-parted calyx, usually 

 small. Within, there appear the five corolla lobes, turned back 

 around the pedicel of the flower when it opens. Next are five 

 curious hood-shaped appendages of the corolla, known as the 

 corona. Inside of each hood is a horn-shaped process, while 

 the stamens fuse together into a tube around the central 

 fruit-rudiment. \\'hen an insect visits the flower in search of 

 honey, it catches its legs in grooves between the hoods of the 

 corona, and in attempting to escape must drag its feet over a 

 part of the stamen where a viscid forked body is located, and this 

 with a couple of pollen-masses attached to it is pulled out of 

 the flower. By means of a bit 

 of silk thread any one can, with 

 proper care, extract the little 

 saddle-bag, thus imitating the 

 work which the flower exacts 

 from its insect visitor. Often 

 bees are not strong enough to 

 jerk their legs free from the 

 cleft in which they are caught, 

 and they may sometimes be 

 seen hanging head-downward 

 from the milkweed flower, de- 

 spondent or dead. 



The different sorts of milk- 

 weeds in INIinnesota may be 

 identified by the shapes of 

 their leaves, the colors of their 

 flowers and the surfaces of their pods. One milkweed, com- 

 mon on prairies, has bright orange flowers, and this sort is 

 known as the butterfly-weed. Its leaves are alternate and hairy 

 and the pods stand erect and are covered with fine hairs. 

 Another group of milkweeds has the flowers purple and the 

 leaves opposite. Here are classified the purple milkweeds, 

 with stout, smooth stems two feet or more in height and leaves 

 of an elongated, pointed oval shape. They are found in dry 

 fields. The swamp milkweed is similar in appearance, but has 

 smaller clusters of flowers and slenderer willow-shaped leaves, 

 usually ciuite smooth. It is to be looked for in swamps or 



Fig. 173. Swamp milkweed. After Britton 

 and Brown. 



