ILLUSTRATIONS OF INDIAN BOTANY. 203 



''The characters of these three genera will then stand thus:— 



''Rivea.^Fruit indehiscent. Ovary 4-celled. Stigmas 2, linear, cylindrical or lamellate 

 ''Argyreia.^-^Frmt indehiscent. Ovary 4-celIed. Stigmas capitately 2-lobed. 

 "Le^^^omza.— Fruit indehiscent. Ovary 2.celled. Cells 2-seeded. Stigma capitately 2-Iobed 



Moor croft 



Maripa, Legendrea, Marcellia, Blinkworthia 9 Humberiia 



bed by Lettsomia^ along with some 

 (Ch.), A. aggregata (Ch.), A. festiva 



(Ch.), A. elliptica (Ch.). Our genera will then possess precision of outline very favoura- 

 ble for the determination of their species: as they now stand, that is wanting, and deter- 

 mination is consequently most difficult, whence we now find species of Argyreia, as here limited, 

 referred to Rivea, Argyreia, and even to Ipomoea.*" 



my 



Madras Journal 



Analytica'' of the Peninsular genera and species, which I often found of infinite service, prior 

 to the appearance of De Candolle's 9th volume, and which I still find a valuable adjunct to the 

 larger work in the determination of difficult species, and at all times more convenient for 

 ready reference. In the suplementary plate I have introduced analyses of as many of the genera, 

 as I could make it accommodate. 



Choisy'^s tribe Cuscutece is considered by many Botanists, and not without reason, a distinct 

 order. It differs widely in habit, being parasitical and leafless, and in having, moreover, a series 

 of scales within the tube of the corolla which, it is presumed, may be viewed as an inner row 

 of stamens. On this point I feel very doubtful, as we find similar appendages in many other 

 plants where no such origin is suspected, and moreover because I find them wanting, in one I 

 published in my Icones, under the name of Cuscuta arabica. The habit is dissimilar, the 

 embryo is very different, and the scales are wanting in ConvolvulacecBj all legitimate grounds 

 for viewing them as distinct; but still, as they have always been united, I feel disposed for the 

 present to retain them here. 



CLAVIS ANALYTICA of the ConvohulacecB of the Peninsula of India, by George 

 Walker-Arnott, Esa. a.m,, f.l.s. Sc u.s, Edin.; communicated^ with observations a?id 

 figures^ by Dr. Wight. 



to THK editor of the MADRAS JOURNAL OF LITERATURE AI7D SCI£>'C£. 



Sir — The subjoined Clavis Analytica of the Peninsular Convolvulace£B (prepared and 

 communicated to me by Gr. Walker- Arnott, Esq.) I hope will prove as useful to your bota- 

 nical readers as I have found it, in determining the species of that beautiful, but difficult, 



and hitherto ill-understood, family of plants. I may here premise, that I have met with 

 one or two errors in the first two genera, two or three species of Hivea being referred to 

 Argyreia^ which^ however, is of little consequence, as tLe precision of the generic characters 



w 



nis Memoir. Mr 



s according to M. Choisy's deter- 

 that gentleman when elaboKiting 



M. Choisy'^s Memoir on the Indian Convolvulaceoe is inaccegsible (b 

 •ciety^s transactions), I have got a loan of it from our friend Sir W. J. 



Analytica, adapted solely to the Peninsular species, which I have made out from his specific 

 characters for my own use. You of course understand, that in the Clavis I reject all characters 

 (good or bad) that are not essential to your making out the plant : it is possible, therefore, that 

 ere this you may have got some new ones, in which case they, by the Clavis, may appear to 



comeide 



successive steps of operati 

 . the second to the tBrd, & 



The species, Ipomea ohscura, has been selected as a favourable example, from its going 



through so many successive steps. These, when pnt together, form a very complete character : 



