MONOCOTYLEDONS AND DICOTYLEDONS 



277 



ray-flowers is the broad expanse supplied by a very much 

 broadened axis, aM known as the disk (Fig. 261, A), which 

 is closely packed with very numerous small and regular 

 tubular flowers, known as disk-flowers (Fig. 201, e). 



Fig. 262. The common dandelion ('7V/7'a,7-a^'/;«): I, two flower stalks ; in one the head 

 is closed, showing the double involucre, the inner erect, the outer reflexed, in the 

 other the head open, showing that all the flowers are strap-shaped; J, a single 

 flower showing inferior ovary., pappus, corolla, stamen tube, and two-parted style; 

 3, a mature akene; 4, a head from which all but one of the akenes have been re- 

 moved, showing the pitted receptacle and the prominent pappus beak. — After 

 Stf.asel'kuee. 



The division of labor among the flowers of a single head 

 is plainly marked, and sometimes it becomes quite com- 

 plex. The closely packed flowers have resulted in modify- 

 ing the sepals extremely. Sometimes they disappear en- 

 36 



