292 



DICOTYLEDONS. 



Fig. 397. 



scales. ) The stamens are united by their anthers into a tube 

 (syngenecious) which closely surrounds the style. (In am- 

 brosia the anthers are sometimes distinct.) The style in pushing 

 through brushes out some of the pollen from the anthers and 

 bears it aloft as in the bell-flower, but the stigmatic surface is 

 not yet mature and expanded, so that close pollination cannot 

 take place. There are usually no stamens in the ray-flowers. 

 The ovary is composed of two carpels, as is 

 shown by the two styles, but there is only one 

 locule, containing an erect, anatropous, ovule. I 

 The floral formula for the composite family\ 

 then is as follows: Ca5, C05, A5, G2. 



555. The rattlesnake- weed (Hieracium veno- 

 sum) is an example of another type, with only „ f _ , 



one kind of flower in the head, the true ligu- flower - ( Vines ) 



late flower. The hawkweed, or devil's 

 paint-brush (H. aurantiacum) is a re- 

 lated species, which is a troublesome 

 weed. The dandelion and prickly 

 lettuce are also members of the ligulate- 

 flowered composites. A number of 

 the composites have only tubular 

 flowers, as in the thoroughwort (eu- 

 patorium) and everlasting (anten- 

 naria). 



566. The extent to which the union of the 

 parts of the flower has been carried in the 

 composites, and the close aggregation of the 

 flowers in a head, represent the highest stage 

 of evolution reached by the flowers of the 

 angiosperms. The composites stand just 

 above the bell-flowers and lobelias, at the 

 termination of a series. The teasels show 

 a relationship to the composites in the aggre- 

 gation of the flowers in a head. But the con- 

 solidation of the parts of the flower has not been carried so far, and the 

 flowers are each separated by an "epicalyx " in the form of a minute cup- 

 shaped involucre. The teasels stand at the termination of another series in 



Fig. 398. 

 Rattlesnake-weed (Hieracium ve 

 nostim). 



