200 ILLUSTRATIONS OF INDIAN BOTANY. 



CXVIL— CONVOLVULACE^. 



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Pew orders have proved more troublesome to Botanists than this large and very natural 

 family of plants, while its numerous and beautiful species have made it a great favourite. The 

 great difficulty which has always attended the investigation of its species has originated, not 

 so much in their discrimination as in the correct limitation of the genera to which they require 

 to be referred, a point on which, for a long time, no two Botanists could agree. M. Choisy in 

 his memoirs on the order (Mem. Soc. Phys. Genev. Vol. vi,), and subsequently in his monograph 

 in De CandoUe's prodromus, has done something towards removing that obstacle to our more 

 intimate acquaintance with the species, but he has still left much for future Botanists to accom- 

 plish. Of this he himself seems well aware as he "recommends and exhorts the reader not 

 readily to relinquish the work of investigating a species of Convolviilacece^ nor too readily to 

 cut the Gordian Knot by creating new species and proposing new names, which may render the 

 Synonomy, already very obscure, still more so. If the plant under examination, says he, is not 

 found among the Ipomwas, then try among the Argyreias, then among the Jacguemontias, and 

 it will perhaps be easier.'" Had he not felt conscious of the imperfections of his work, he 

 could scarcely have deemed it necessary to introduce such an exhortation. The fact seems 

 to be, as I have (to a limited extent) ascertained by the examination of authentic specimens of 

 a number of his species, that he had constructed his generic characters from single species and 

 has added on others, without sufficient examination to ascertain whether they corresponded, 

 and hence has resulted, on numerous occasions, inextricable confusion, unless his own specimens 

 be re-examined to verify his generic determinations. His generic characters, if sufficient for 

 the purpose, are simple enough and for the most part, with the aid of a microscope of moderate 

 power, easily made out, but the species referred to them have not been generally subjected to 

 that test. The question then occurs, are the characters sufficient? This I will not attempt to 

 answer, but whether or not, I feel quite certain the most has not been made of them ; they are 

 artificial, based on the ovary, and will be found useful in practice, but I am convinced, from 

 my own examinations, that that organ has rarely been examined. I have felt it necessary to 

 introduce these remarks to warn the Indian Botanist who undertakes, with the aid of Choisy's 

 monograph, to name his species of ConvolvulacecB, to expect many difficulties and some disap- 

 pointments. On the correctness or otherwise of the principles adopted I offer no opinion, content- 

 ing myself with the results as shown by their fitness for practical application. As applied on 

 the large scale of the whole order, they will probably be found defective; as limited to the 

 Indian flora, I have, with some slight corrections, found them so useful that I now regret not 

 having re-examined, with that special object in view, all those named in the subjoined conspectus, 

 so as to have enabled me, if not to recast the whole, at all events to indicate those which have 

 been referred to wrong genera. The order is one of great extent, and also in very many 

 instances of great beauty. Lindley gives 43 as the number of its genera, and 660 species. 

 Additions have been since made to the species, but it is my belief the genera, as now constructed, 

 must be reduced rather than augmented, but at the same time it is my impression that when 



constructed on more philosophical principles, the number will be increased beyond the pre- 

 sent standard. "^ 



J 



Character of the Order. Calyx 5-sepaled: sepals persistent, equal or unequal, arrang- 

 ed in a single, double, or triple series, often enlarging with the fruit. Corolla raonopetalous, 

 hypogynous, regular, with the hinb, 5-pIaited or 5-lobed, twisted in aestivation. Stamens 5, alter- 

 nate with the lobes of the corolla; filaments often unequal, dilated at the base; anther long, 

 adnate, sagittate, 2-celled; pollen granular, spherical or annular. Nectary annular, embracing 

 llLXr . TP «^ ^««t species Ovary usually simple, 2-4-celled,\arely partially, or 

 7T^l' o^e-celled, occasionally double or qaudruple; each cell with one or two erect ovules; 

 Jermina i;r.iT;r''\^'/r deeply bifid, rarely double; stigma acute, flattened, or globose, 

 SscW L drv h'L"'^^ of the style, hence, 2-lobed on a single style. F;uit capsular, viriously 



vaW^' SeeKbt • ' 1^ ^^''''"^^-^''l^''^' ^^"« 1-2-seeded; dehiscence of the capsules 

 valvate. Seed aubtnangular, rounded on the back, glabrous or villous; testa usually hard; 



