22S 



COMPOSITy^. 



[chap. 



N.B. The ovary is invariably one-celled, with a soHtary 

 erect ovule. The number of carpels forming the pistil is 

 inferred from the bifid stigma. From analogy it is inferred 

 also that the calyx consists of five sepals. The limb, how- 

 ever, is frequently wholly absent {obsolete)^ as in the Umbel- 

 late Family ; while in some genera it is represented by 

 scales or hairs, forming z. pappus, which persists and crowns 

 the ripe fruit. 



In Zinnia the pappus is reduced to one or two bristles. 



Compare, with respect to the form of the corolla of the 

 florets of the flower-heads — 



Zinnia, with disk and ray (see p. 36) ; Venioma cinerea 

 (an annual weedy Flea-bane, with small flower-heads, com- 

 mon in waste places), with all the florets regular {tubular^, 

 resembling those of the disk of Zin7iia in form ; Sonchus 

 (a weed of cultivated ground, with yellow flower-heads), with 

 all the florets irregular (ligulafe), resembling those of the 

 ray of Zinnia in form; Echinops echinaius (with terminal, 

 globose, spiny flower-heads), each floret enclosed in a dis- 

 tinct involucel. 



When all the florets of a flower-head are tubular, the 

 flower-head is discoid; if the florets of the ray be ligulate, 

 the flower-head is radiate. 



