24 DIANDRIA.— MONOGYNIA. 



21. COLLINSONIA. Horse-weed. Labiatce. 

 C. canadensis : leaves broad-cordate, ovate, glabrous ; 



teeth of the calyx short, subulate ; panicle terminal. 



compound. 

 HAB. Among rocks, in rich soil. Aug. V-. Smooth: 



leaves on long or short footstalks ; fl. dull yellow. 



22. CIRCiEA. Enchanter's nightshade. Onagroz. 

 1. C. lutetiana (Z. canadensis: stem erect ; leaves ovate, 

 remotely toothed, opaque, nearly smooth. 

 HAB. Shady woods. July— Aug. It. Stem 1—2 feet 

 high, simple ; fl. in racemes, pedicellate, reddish- 

 white ; fruit hispid. 

 I. C.alpina: stem branched, very smooth, often pro- 

 cumbent ; leaves broad-cordate, membranaceous, 

 acutely toothed, shining. 

 HAB. On barks of trees and wet mossy rocks. Aug. %. 

 Very s?nooth, 6 — 8 in high ; leaves very broad, sub- 

 diaphanous ; fruit pubescent. 



23. LEMNA. Duck's-meat. Naiades. 



1. L. trisulca: fronds thin, elliptical-lanceolate, caudate 



at one extremity, at the other serrate, ; roots solitary. 

 HAB. Pure stagnant waters. 0. Fronds laterally proli- 

 ferous, and appearing cruciate ; root a solitary fibre, 

 caiyptrate at the extremity. 



2. L. minor : fronds nearly ovate, compressed ; roots 



solitary. 

 HAB. Stagnant waters. ©. Fronds a line or a line and a 

 half long, succulent, aggregated. 



3. L. gibba : fronds obovate, nearly plane above, hemis- 



pherical beneath ; roots solitary. 



HAB. Stagnant waters. 0. Fronds as large as the prece- 

 ding, gibbous, pellucid and reticulated beneath. 

 I. L. polyrrhiza : fronds obovate-roundish, compressed ; 

 roots numerous, fasciculate. 



HAB. On stagnant waters, often with No. 2. ©. 3 — 4 

 lines long, rarely proliferous. 



24. CRYPTA. Portulaceaz. 



C. minima. 



HAB. Borders of ponds, and banks of rivers. ? Aug, 

 minute, Prostrate and creeping, with the branches 

 assurgent; leaves oppos. cuneate ; fl. minute, axill. 



