THE CLASSES POLYDELPHIA AND SYNCENESIA. 



167 



elongated into a tendril or cirrhus (Fig. 185). The prevailing colours of the corolla 

 are yellow or red. 



CLASS XVIII. POLYDELPHIA. 

 This class consist* of one genus, Hypericum or St. John's Wort, and eleven genera, 



Fig. 353. Polydelphia Polyandria. 



and has the stamens divided into three, four, or more sets (Fig. 220). 

 wise of interest. It belongs to the order Polyandria. 



It is not other- 



CLASS XIX. SYNGENESIA. 



This is the largest class of plants in every Flora, and is one of exceedingly well- 

 defined characters. It is also one of some difficulty to the young botanist in determining 

 the species, and even some of the genera ; but the mere class-characters are, even to 

 him, of most ready discernment. Its distinguishing feature is the union of the anthers 

 (not necessarily of the filaments also) into a tube through which the pistil passes 

 (Fig. 222). The flowers are also arranged on a capitulum or head, and, in many 

 instances, those of the margin or ray differ in size, or other particulars, from those of 



Fig. 354. 

 Polygamia Equalis. 



Fig. 355. 

 Pelygamia Superflua. 



Fig. 356. 

 Polygamia frustanea. 



the centre or disk ; and hence the flowers of the head are frequently divided into florets 

 of the ray and florets of the disk. The whole florets are surrounded by an involucre 

 of bracts, and each separate floret has a small calyx, which is commonly chaffy. The 

 part upon which the flowers are placed is called the receptacle (Fig. 193). There are 

 forty-one genera, and one hundred and thirty-three species. 



This class is divided into three orders. The first is Polygamia Equalis, in which all 

 the flowers are perfect, having five stamens and one pistil, and producing one seed. 

 It contains 22 genera and 71 species, and is subdivided into three parts, accord- 

 ing to the form of the corolla. Twelve genera have all the corollas strap-shaped. 

 Such are the Ciohorium or Chicory, the root of which is ground to powder, and used as 

 a substitute for Coffee ; Lactuca or Lettuce, which in its wild state is poisonous, but 



