190 Common CAtJAbiAit wiLb tLANTS. 



Var. ineaFna'tum, Watson, has the spikes more slender 

 and elongated, nodding, 



Var. inea'num, Koch, is 6-12 inches high, with small 

 leaves more or less flocculent-hoary underneath, and short 

 spikes. Chiefly easttcard and N. W. 



6. P. Pennsylvan'ieum, L. Sheaths not fringed. Stem 

 1-3 feet high, the upper branches and the peduncles bristly 

 loith stalked glands. Spikes thick, erect. Stamens 8. Acheue 

 flat. — Low open grounds. 



7. P. Persiea'rla, L. (Lady's Thtjmb.) Sheaths with a 

 somewhat ciliate border. Stem nearly smooth, a foot or more 

 in height. Leaves with a dark blotch on the middle of the 

 upper surface. Spikes dense, erect, on naked peduncles. 

 Stamens 6. Achene flat or 3-angled, according as the stig- 

 mas are 2 or 3. — Very common near dwellings in moist 

 ground. 



8. P. amphib'ium, L. ("Watek. Pebsicaeia.) Spike of 

 flowers dense, oblong, showy, rose-red. Stem floating in 

 shallow water or rooting in soft mud, nearly glabrous. 

 Leaves long-petioled, often floating. Sheaths not bristly- 

 fringed. Stamens 5. Stigmas 2. — In shallow water, mostly 

 northward. 



9. P. Muhlenberg' 11, Watson, differs from the last in 

 being rough with appressed hairs all over. — Ditches. 



10. P. Hartwrlght'll, Gray, is distinguished from P. 

 amphibium by its foliaceous and ciliate sheaths. — Muddy 

 margins of ponds and lakes. 



11. P. hydFOplpSFOl'des, Michx. (Mild Water-Peppeb.) 

 Stem slender, 1-3 feet high, in shallow water. Leaves narrow, 

 roughish. Sheaths hairy and fringed with long bristles. 

 Spikes slender, erect, pale rose-coloured or whitish. Stamens 

 8. Stigmas 3. Acheue 3-angled. — In shallow water. 



12. P. acre, H. B. K. (Water Smartwbed.) Sheaths 

 fringed with bristles. Leaves transparent-dotted. Stem root- 

 ijig at the decumbent base, 2-4 feet high, in shallow water 

 or muddy soil. Leaves narrow, taper-pointed. Spikes 



