122 DICOTYLEDONOUS PLANTS. 



adhering to the ovary ; limb 4-lobed. Petals none. Nuts 4, 

 compressed or eubglobose, 1-seeded. 



Monoecia. Polyandria. 



* Flowers octandrous. 



1. M.'spicatum Linn. .- leaves verticillate, pinnately divided ; lobes 

 capillary ; spike terminal, nearly naked ; floral leaves shorter than the 

 flower ; lower ones subserrate and mostly very entire. 



HAB. In water. Can. and N. S. Aug., Sept. It. Stem slen- 

 der, branched. Leaves in whorls, by fours, pectinate. 



Water Milfoil. 



2. M. verticittatum Linn. : leaves verticillate, pinnately divided ; 

 lobes capillary, opposite ; spike terminal, leafy ; floral leaves all pin- 

 nately divided, much longer than the flowers, and scarcely distinct 

 from the leaves. 



HAB. In water. Can. to Car. July. If. Upper flowers some- 

 times perfect. 



** Flowers hexandrous. 



3. M. heterophyUum Mich. : leaves verticillate, pinnately divided into 

 capillary lobes ; spike terminal, nearly naked ; floral leaves opposite, 

 vate, acute, coarsely serrate, longer than the flowers. Potamogcton 

 certicillatum Walt. 



HAB. In water. N. S. to Geor. July. If. -Stem simple. 

 Flowers purple. 



*** Flowers tetrandrous. 



4. M. capittaceum Torr. : Jeaves all capillary-pinnate ; flowers axil- 

 lary, opposite and alternate, tetrandrous, mostly perfect j fruit quad- 

 rangular, formed of 4 cylindiical seeds. 



HAB. Ponds. July, Aug. If- Floating-stem branched, di- 

 chotomous. Leaves hair-like. 



5. M. ambiguum Nult. : leaves petiolate, pinnate, the lowest ones 

 capillary ; emerging ones pectinate ; uppermost nearly entire, subser- 

 rate ; anthers partly oblong ; fruit quadrangular. 



b. limosum Nutt. : stem rooting, erect ; leaves rigid, partly entire, 

 or divided above, mostly trihd ; segments setaceous and acute. 

 Purshia humilis Raf. ? 



HAB. Ponds. N. J. July. If. Floating in extensive masses. 

 Stem dichotomous. Leaves attenuated so as to appear petioled, 

 pectinately pinnatifid. Floicers axillary, solitary, sessile. 

 yar. b. Miry shores of the Delaware, N. J. Stem erect, 24 

 inches high, decumbent and rooting. Leaves rigid and spreading, 

 very narrow, setaceous and acute. Flowers as in the preceding, 

 but the anther's are roundish. 



6. M. teneUum Big. : stem simple, nearly leafless, erect, somewhat 

 rooting at base ; leaves in form of scales, alternate, entire ; upj^r ones 

 bearing flowers in the axils ; spike terminal, interrupted; flowers alter- 

 nate. 



