APPENDIX. No. V. 435 



The second is perhaps not distinct from Melastoma decumbens, of tlie same 

 author.* 



The third and fourtli are new species referable to Rhexia, as characterised 

 by Ventenatjf though not to that genus as estabhshed by Linneus ; and in 

 some respects differing from the species tliat have been since added to it, all 

 of which are natives of America. 



In the original species of Tristeinma\ there are, in the upper part of the tube 

 of the calyx, two circular ciliated membranous processes, from which the 

 name of the genus is derived ; the limb of the calyx itself being considered as 

 constituting the third circle. The two circular membranes are also represented 

 as complete in T. hirtum. 



But in the species from Congo, which may be named T. incompletum, only 

 one circular membrane exists, with the unilateral rudiment of the second. 



The rudiment of the inferior membrane in this species, points out the rela- 

 tion between the apparently anomalous appendage of the calyx in Tristemma, 

 and the cUiated scales irregularly scatteretl over its whole surface in Osbeckia ; 

 the analogy being estabhshed by the intermediate structure of an unpublished 

 plant of this order from Sierra Ltxjne, in Sir Joseph Banks's herbaiium, in 

 wliich the neai'ly similar squam£e, though distinct, are disposed in a single 

 complete circle ; and by Melastoma octandra of Linneus, in wliich they are 

 only four in number, and alternate with the proper divisions of the calyx. 



The two species here referred, though improperly, to Rhexia, agree with a 

 considerable part of the species published in the monograph of that genus by 

 "M. Bonpland, and with some other genera of the order, in the jjeculiar manner 

 in which the ovarium is connected with the tube of the calyx. This cohesion, 

 instead of extending uniformly over the whole surface, is Umited to ten longi- 

 tudinal equidistant lines or membranous processes, apparently originating from 

 ihe surface of the ovarium ; the interstices, which are tubular, and gradually 

 i:arrowing towards the base, being entirely free. 



The function of these tubular interstices is as remarkable as their existence. 



In Melastomaceae, before the expansion of the coroEa, the tops of the fila- 

 ments are inflected, and the antherae are pendulous and parallel to the lower 

 or erect portion of the filament ; their tips reaching, either to the line of com- 

 plete cohesion between the calyx and ovarium, where that exists ; or, where 



* Op. cilat. l,p.69,l.49. ^ Mem. <fe I'lnstitut. sc. ph^s. ISOl, prem. semest. p. \l. 



+ Tristemma virusaaa, lent, Choix de Plantes 35. 



