230 



ILLUSTRATIONS OF INDIAN BOTANY 



POSTSCRIPT TO JlSCLEPMDE^. 



^ 



An unlooked for occurrence caused some of the preceding articles to be written more hurriedly tha» 

 was quite consistent with careful study of the subjects to which they refer. Asclepiadeas was one of these. 

 Owing to that circumstance I was at the time of writing prevented satisfying myself of the accuracy of some 

 former observations, regarding which I felt somewhat doubtful. Since the article passed through the press^ 

 I have been permitted to return to the subject, and now think it advisable to add a brief Postscript appertaining 

 to the tribe Periplocece. 



The investigation of the pollen of the members of this tribe is by far the most diflBicult of the order, but 

 fortunately, an exact knowledge of this part of the organization does not seem so indispensable to the discri- 

 mination of its genera, as in the other tribes. In some of the genera I find the pollen loose and granular^ 

 even in the anther of the flower-bud, in others it is coherent in the anther but, about the time of expansion 

 of the flower when the anther cells open, it loses its cohesion and becomes attached to the corpuscule in a 

 loose granular form; while in others, as Hemidesmus and Brachylepis it still presents the form of masses after 

 they have left the anther cell. The circumstance of so many presenting granular pollen after the expansion 

 of the flower, combineJ with the difficulty of examining it in the early stages of the flower-bud, lead me to 

 the conclusion that an exact knowledge of this part of the organization is less necessary in the limitation of 

 the genera of this tribe than in those of the others. I have not a genuine species of Periploca to examine 

 to ascertain how it is in that genus, but infer, from the circumstance of Decaisne having transferred one of 

 my Streptocaulons to it, that it is the same in both* Finlaysonia I have examined, but scarcely feel satisfied 

 with the result, as regards the pollen, but in all other points it comes so near my Siveptocaulon that I now 

 ■uspect the latter ought to be reduced and its species referred to the former genus. 



As already remarked, Decaisne, following Falconer, however, has transferred one of my species of Slrepto- 

 caulon to Periploca. To this transfer I, with all defl^erence, beg leave to demur, unless they take the rest along 

 with it, and at once reduce my genus. To this I should not object, as I now think the two genera too nearly 

 ;inied. Slreptocaulon was, in the first instance, constituted to receive a number of Asiatic plants only differing 

 from Penploca in having glabrous anthers; those of Periploca being surmounted by a dense tuft of hair. The 

 genus therefore essentially rests on these two circumstances — Asiatic origin and glabrous anthers — Periploca 

 claiming European or African 6rigin, and having hairy anthers. 



These characters I do not now think entitled to generic value, and believe that the species of both genera 

 miglit all be associated under one (with the aid of a section), but so long as Slreptocaulon retains a place 

 in the^ botanical system, I hold that S, calophjUum must remain with it, at all events, cannot be transferred 

 to Periploca^ as its admission into that genus breaks down the only characters by which the two are kept dis- 

 tinct, being an Asiatic plant and having glabrous anthers. 



I regret not having a specimen of Periploca gr<Bca, the type of the genus, with which to illustrate my posi- 

 tion by giving a figure of it side by side with StrepL calophi/tlwn, to show by contrast the difference, but to 

 compensate as far as I can, I give, in an additional plate, generic analyses of that plant and of two species of 

 Slreptocaulon, examined by Decaisne and retained by him in that genus, which will show that there is no 

 difference between them and the excluded one ; and in lieu of original dissections, I copy some parts of Lamark's 

 analysis of P, graca. 



Having still 



some room left, I have, in the hope of rendering that supplementary plate more useful, 

 introtluced dissections of some other genera of this tribe. These are all more or less perfect, but rather too 

 crowded, being anxious to illustrate as manv genera as I could within the small space at my disposal. The 

 subjects introduced into that plate are: three species of Slreptocaulon, Periploca grmca, Finlaysonia, Brachylepis, 

 IJecalepis, Lrypioltpxs, and Crypiostegia. Hemidesmus, Brachylepis, and Decalepis are all nearly allied genera; 

 Cryptostegia^and tryptolepis are also very nearly allied ; while Streptocaulon, Finlaysonia. and Periploca are so 

 much alike that it is now my belief they might be advantageously united 



EXPLANATION OF PLATE 182 or 155 



1. 

 2. 

 3. 



4. 



5. 



Streptocaulon calophyllum. (R. W.) 

 tomentomim. "" 



extensum. 

 Periploca graeca. 



Finlaysonia obovata^ 



{R. W.) 



(R. W.) 



(Linn.) 



(Wall) 



6. Decalepis HamiltoniL (W. & A.) 



7. Brachylepis nervosa. (W, & A,) 

 K Cryptolepis Buchanani. (R. B.) 

 9. Cryptostegia grandiflora. (R. B.) 



EsD OF Second Volume. 



3PKi>'iEU EY P. R. Hi:>T 



■AMERICAN MISSION PRESS, MADRAS 



