252 



FAMILIES OF FLOWEEING PLANTS. 



aceae : that is, the flowers are aggregated in an involucrate head ; but 

 there is this difference, that in the 

 Compositae proper only part of 

 the flowers have strap-shaped 

 corollas, the others being tubular 

 and inconspicuous, like those in 

 the " center " of a so-called daisy 

 flower. In some tribes, indeed, 

 the flowers are all tubular. On an 

 examination of any Composite we 

 can readily understand why this 

 family illustrates the highest de- 

 velopment among flowering plants, 

 on the theory that separation of 

 parts is an indication of primitive 

 structure. For here the anthers 

 and filaments are united into a col- 

 umn; the corolla forms a tube; the 

 calj^ is in such intimate adher- 

 ence to the ovary that it may be 

 said to have disappeared ; the 

 ovary is one-seeded : the flowers 

 are aggregated in a close head; . , ,^ ^ ,c- , ,/ 



J I -P" n 1 1 , 11 Fig. 223. A native species of golden-rod {Sohdago 



and the floral bracts are crowded ^„„^^^, After Britton and Brown, 111. F1. Northeast. 



into a calyx-like involucre. u. s. 



Fig. 224. A western composite allied to the " black-eyed Susan " {Ratibida 

 colutnnaris). After Britton and Brown, 111. Fl. Northeast. U. S. 



And thus, having found our way through the maze of plant fami- 



