A GUIDE AND KEY TO AQUATIC PLANTS 



51 



20. Leaves all basal or arising from points along 21. 

 a horizontal stem. 



20. Leaves distributed along stem 26. 



21. Leaves coming off at points along a horizontal stem. 24. 



21. Leaves basal to flower stalk 22. 



22. Leaves with several prominent rib-like veins Alismaceae, p. 72. 

 running from base to apex (fig. 18). 



22. Veins of leaves not prominent 23. 



23. Leaves with blunt lobes; flower conspicuous, purple, Pontederia, p. 107. 

 not on a fleshy axis enclosed in a leaf-like sheath 



(fig. 19). 

 23. Leaves usually with sharp lobes; flowers individually Peltandra, p. 103. 

 inconspicuous, on a fleshy axis enclosed in a leaf- 

 like sheath (fig. 20). 



Figure 18. 



Figure 19. 



Figure 20. 



24. Leaves small (less than 0.5 dm. long), coming 25. 



off from slender, prostrate stems. 

 24. Leaves large (2 dm. long or more), coming Nuphar, p. 116, 

 off of stout underground stems (fig. 21). 



25. Leaves toothed; veins of leaf irregular (fig. 22) Centella, p. 131. 



25. Leaves entire; veins of leaf nearly parallel (fig. 23). __ Heteranthera, p. 106. 



Figure 21. 



Figure 22. 



Figure 23. 



