400 



Minnesota Plant Life. 



lar flowers centrally, and the thistle furnishes one in which all 

 the flowers are tubular. 



In composite flowers the stamens generally have their pollen- 

 bearing portions fused to- 

 gether into a ring, while their 

 ^^^^^^^ stems are free. The fruit- 



- ^ ; rudiment is composed of two 



*> 1* carpels, with a single cham- 



ber in which a single seed 

 matures. The calyx is always 

 fused with the surface of the 

 fruit-rudiment, and in a great 

 many varieties the calyx pro- 

 duces a bristly or scaly series 

 of appendages for distribut- 

 ing the fruits in air currents. 

 The well-known parachutes 

 of the dandelion are such 

 areas, with the margins frayed 

 out into circles of little bris- 

 tles. Sunflower fruits are 

 provided with a pair of scales 

 similarly derived from the 

 calyx. When the fruits are 

 enclosed in burs, the calyx 

 sometimes, as in the cockle- 

 burs, develops this flying ap- 

 paratus but poorly, while in 

 other instances, as in the bur- 

 docks, flying appendages are 

 produced upon each fruit, 

 probably reminiscences of an 

 earlier condition when the 

 bur-method of distribution 

 had not been perfected. The 

 modified, aeronautic calyx of 



FIG. 193. Chrysanthemum in flower. After 4-U e r n m n O m' t P flower k 

 Miller. Bull. 147, Cornell Ag. Expt. Sta- 



tion - known as pappus. 



