A GUIDE AND KEY TO AQUATIC PLANTS 



49 



12. Base of petiole of leaf expanded into a sheath 13. 

 which encircles stem at junction. 



12. Base of petiole not expanded (fig. 8) Proserpinaca, p. 129. 



13. Leaves, at least the upper ones, only once compound Sium, p. 131. 



(fig. 9) 

 13. Leaves twice divided 14. 



14. Leaflets narrowly linear, untoothed; plants Ptilimnium, p. 131. 



annual (fig. 10). 

 14. Leaflets wider, toothed; plants perennial (fig. Cicuta, p. 131. 



11). 



Figure 9. 



FlGDBB 10, 



Figure 11, 



