CL. I.] 1. HIPPUIIIS VULGARIS. 345 



Equisetum palusire, brevibus foliis polyspermum, C. Bauhluy 



15. Parkin's Theatr. 1200. 

 Pinastella, Dill. Giess. Jpp. 168. Biuvb. Hal. 261. 

 Limnopeuce, V. Cord. Hist. p. 150. Vaill. Mem. dc Paris, 



1719, p. 15. t. 1. f. S. Hall. Stirj). n. 1572. 

 Hippuris vulgaris, Linn. Fl. Dan. 87. Engl. Hot. 76'J. 



Gdrtn. Friict. t. 84. Richard in Ann. da Mu^-. J3. t. '30. 



f. 8. 



Affinity. 



The first authors who arranged this plant in a natural or- 

 der, placed it beside Ceratophyllum^ Myriopliyllum^ Zanni- 

 chellia, and immediately after it they placed Pilnlaria, {Ray, 

 syn. p. 136.) Linna?us also placed it along with similar 

 plants in his 15th tribe, which he called Inundates, {Giseke 

 Ord. Nat. p. 327.) Batsch followed the same plan (Tab. 

 Ajffin. Regn. Veget. p. 161.), denying at the same time, very 

 improperly, to the Inundatae, the albumen in the seed. And 

 Jussieu opened with this plant his family of the Naiada?, 

 placing Chara immediately after it, {Jussieu, Gen, Plant. 

 p. 18.) But Adanson was the first who thought of a higher 

 place, for he placed his Limnopeuce among the Elaeagna> be- 

 tween Thesium and Cynomorium, {Adanson, Famill. 2. 

 p. 80.) More lately Jussieu has approved of this arrange- 

 ment, {Ann. du Mus. 3. p. 323.) ; and De Candolle has 

 placed the plant among the Onagrae, {Fl. Franc. 4. 415.) 

 Lastly, Nuttal thinks it has no afiinities. 



But when we direct our attention to the existence of a cen- 

 tral bundle of spiral vessels, and to the slits on the surface, 

 and recollect the law, that essential differences of internal 

 structure almost always correspond with differences in the 

 formation of the seed, and in external relations (170.), Adan- 

 son's idea gains considerable strength. If we compare Ela- 

 agnus and Hippophde with this plant, the formation of the 

 seed, and the position of the embryon, on which most de- 

 pends, agree completely, (171.) Instead of the nut in oui- 

 plant, these others have a drupe. The calyx, whitli in 

 the Hippuris is not unfolded, consists in Elrrngnus of four 



