PHANEROGAMIA 



505 



and six (6 + 0) stamens. Mheum, Rhubarb, has also a calyeoid perigone and nine 

 (6 + 3) stamens. 



Fig. 455.— Rheum qffteiimle, greatly reduced. (After Baillon.) 



Geographical Distribution. — The Polygonaceae are chiefly found in the 

 North Temperate Zone. Bumex acetosa, Sorrel, contains a large amount of potas- 

 sium oxalate, and is on that account esteemed as a vegetable and often cultivated 



