238 



PLANT STRUCTURES 



The simple character of these forms is indicated by their 

 aquatic habit and also by their flowers, which are mostly 

 naked and with few sporophylls. A flower may consist of 

 a single stamen, or a single carpel ; or there may be several 

 stamens and carpels associated, but without any coalescence 

 (Fig. 220, B). 



In the same general line with the pondweeds, but with 

 more complex flowers, are the genera Sagittaria (arrow- 



FiG. 220. Pondwecd (Potamogeton): A, branch with chistor (spike) of simple flowers, 

 showing also the broad floating leaves and the narrow submerged ones; B, a sin- 

 gle flower, showing the inconspicuous perianth lobes (c), the short stamens (a), 

 and the two short styles with conspicuons stigmatic surfaces.— J. after Rbiohen- 

 bach; B after Le Maout and Decaisne. 



