142 MONOECIA— POLYANDRIA. Myriophylluni. 



Equisetum sub aqua repens, foliis bifurcis. Loes. Pruss. 67. 1. 12. 



In ditches and fish-ponds, common. 



Perennial. August, September. 



Herb floating, entirely under water, dark green, copiously branch- 

 ed, 2 or 3 feet long, densely clothed with whorled spreading 

 leaves, 8 in each whorl, all repeatedly cut into fine, linear, equal, 

 acute, roughish segments. Fl. axillary, solitary, sessile, pale 

 green. Fruit armed with 2 spreading lateral spines, and a ter- 

 minal one from the elongated style; all very variable in length. 



2. C. submersum. Unarmed Hornwort. 



Fruit destitute of spines. Segments of the calyx acute, 

 entire. 



C. submersum. Lfnn. Sp.PZ. 1409. Willd.vAA^o. H.BrA020. 

 Engl. Bot.v. 10. t. 679. Fl. Dan.t.5\0. 



C. demersum /3. Huds.4l9. 



Hydroceratophyllon folio l&evi, octo cornibus armato. Faill. Mem. 

 de VAc. des Sc. 29!). t. 15. f. 2. Dill, in Raii Syn. 135. 



In ditches, but rarely. 



By the road from Chichester to Selsey island. Dill. Between 

 Yarmouth and Gorlestone. Mr. D. Turner. 



Perennial. September. 



Like the foregoing, but Vaillant observed the leaves to be smoother, 

 and more divided, having eight segments in all, instead of four. 

 These characters are certainly inconstant. The presence or 

 absence of spines on the fruit, and the segments of the calyx 

 being, as Mr. Sowerby first discovered, sharp and entire, not 

 toothed, are surely sufficient distinctions. Willdenow declares 

 his decided opinion that they are not varieties of each other, 

 though he found the segments of the leaves in both species finely 

 •serrated at the ends. 



438. MYRIOPHYLLUM. Water-Milfoil. 



Linn. Gen. 493. Juss. 18. Fl. Br. 1 021 . Faill. Mem. de tAc. des 



Sc. 306. i. 15./. 3. Gcert?i. t. 68. 

 Pentapterophyllon. Dill. Gen. 125. t. 7. 



Nat. Ord. same as the last. See Grammar, 167. t. 19. 



/ 251. 

 Barr. fl. Cal. of 4 oblong, upright leaves; the outer one 



largest; inner smallest. Pet. 4, obovate, soon falling. 



Filam. 8, capillary, flaccid, longer than the calyx. Anth. 



oblong, vertical. 



Fert.fl. below the others. Cal. and Cor. as in them. Gei-vi. 

 4, oblong, inferior. Styles none. Stigmas downy. Dru- 



