16 



Clavis Analytica of the Convolvulacece 



to ill-understood, family of plants. In publishing it, I fear I am talcing 

 an undue liberty with my friend's manuscript, which he merely intend- 

 ed for my own use, as will appear from the following extract of his 

 letter, but a fellow-feeling for all who have, encountered the dishearten- 

 ing uncertainty attending attempts to unravel the species of this order, 

 induce me to incur the risk of his displeasure, rather than deprive 

 them of so valuable an aid. I may here premise, that I have met with 

 one or two errors in the first two genera, two or three species of Rivea 

 being referred to Argyreia, which, however, is of little consequence, 

 as the precision of the generic characters, will soon lead to their cor- 

 rection. It is proper to add, that these are not chargeable to Mr. 

 Arnott, he having simply reduced to a tabular form the species accord- 

 ing to M. Choisy's determination, adding a few new ones in my collec- 

 tion, not seen by that gentleman when elaborating his memoir. 



" As M. Choisy's memoir on the Indian Convolvulacece is inaccessi- 

 ble, (being printed in a foreign Society's transactions) I have got a 

 loan of it from our friend Sir W. J. Hooker, and as Convolvulacece 

 appears to be a favourite Order of yours, I shall here present you with 

 a Clavis 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 coincide with what they are 

 really distinct from." 



The letters appended to the accompanying figures, shovtf the succes- 

 sive steps of the operation of examining a plant, that at end of first 

 step, refers to the second, the second to the third, &c. The species 

 Ipomea obscura has been selected as a favourable example from its 

 going through so many successive steps. These when put together 

 form a very complete character : thus — " a stems twining — g capsules 

 and sepals moderate sized or small — m flowers not capitate — p leaves 

 cordate — q leaves entire — r flowers two or three — u one to three 

 flowered — v leaves cordate acuminated, stems glabrous or softly vil- 

 lous. I. obscura." 



As it appears not improbable that there are some additional genera, 

 as well as species, not included in this Clavis, natives of, the peninsula, 

 I send along with it M. Choisy's own Conspectus Generum, published in 

 the Annales des Sciences Naturelles, for September 1834, and leave you 

 to determine on the propriety of reprinting it among your selections. 



I remain, &c. 



Robert Wight. 



