400 



Minnesota Plant Life. 



lar tlowers 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 

 carpels, with a single cham- 

 l)er 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 deri^'ed from the 

 calvx. When the fruits are 

 enclosed in burs, the calyx 

 sometimes, as in the cockle- 

 l)urs, develops this flying ap- 

 l^aratus but poorl}', while in 

 (Uher instances, as in the bur- 

 docks, flying appendages are 

 ])n)(luccHl upon each fruit, 

 ])i-()babl\' reminiscences of an 

 earlier condition when the 

 bur-melhod of distribution 

 had not i)een perfected. The 

 J modified, aeronautic cal>x of 



Vie. lilU. ChrysaiitlK-nnim in fowcr. After |]^^^. (_• o m p O S i t C floWCr IS 

 Miller. Hull. 1-17, ConicU As?. I'.xpt. .Sta- 

 tion, known as f^af^f^KS. 



