26G MR. A. W. BENNETT ON THE GENUS nYDKOLEA. 



i 



Eeview of the Genus Hydrolea, witU descriptions of three New 

 Species. By Alfred W. Bennett, M.A., B.Sc., F.L.S. 



(Plate I.) 

 [E^ad November 18, 18G9.] 



The position of the order Hydroleacese has undergone several 

 changes at the hands of botanists. By the older authorities, 

 particiilarly Jussieu, its genera were included among Convolvu- 

 lacese, from which order, however, they are distinguished m a 

 marked manner by their multiovular ovaries, straight embryo, 

 and several other characters of importance. Lindley, in his ^ V e- 

 getable Kingdom,' xmited the order to Hydi*ophyllacese, to which 

 opinion Alph. DeCandolle appeared to incline, from a note ap- 

 pended to the ninth volume of the * Prodromus.' Prof. Choisy, 

 in his monograph of the order, and in the synopsis which he con- 

 tributed to the tenth volume of the ' Prodromus,' clearly showed 

 that this theory is inadmissible, the unilocular few-seeded 

 ovary, parietal placentation, and leaves frequently deeply divided, 

 of the one order, distinguishing it most clearly from the bilo- 

 cular many-seeded ovary, axile placentation, and leaves invariably 

 simple, of the other order ; and that, in accordance with the opi- 

 nion of Eobert Brown and others, the Hydroleacese must be raised 

 to the rank of a separate order. The variation, however, in the 

 mode of dehiscence of the capsule compels its subdivision into 

 two suborders, septicidal in Hydrolese, loculicidal in Nameae. 

 The tendency which exists in several species of Ilydrolea^ to 

 substitute for the normal bilocular a trilocular ovary, would ap- 

 pear to indicate a closer aflBnity to Polemoniaceae than has been 

 generally supposed. Prom Solanaceae they diiFer by their two 

 styles and straight embryo ; from Scrophulariaceae by their re- 

 gular corolla, five equal stamens, and two styles. 



As regards geographical distribution, the order is essentially 

 tropical and subtropical, and especially American. The genus 

 Hydrolea, which is nearly synonymous with the suborder Hy- 

 drolere, ranges from Arkansas to Montevideo, with a few Asiatic 

 and African species, to which I am able to add two, hitherto uu- 

 described, from Tropical Africa, contained in the Kew Herba- 

 rium. The suborder Nameae is exclusively American, the species 

 being mostly natives of Mexico and Peru. The Hydroleace^ are 

 herbaceous or subfruticose plants, the leaves and branches some- 



