Fruit-dispersal in Adenostemma viscosum 
A Biological Study, 
BY 
R. H. YAPP, M.A. 
Professor of Botany in the University College of Wales, Aberystwyth 
With Plate XXIII. 
I N the flower-like inflorescence of the Compositae, as is well known, the 
usual protective function of the calyx is performed by the involucre. 
This being so, the calyx proper is either very much reduced (in a few 
instances entirely suppressed), or else it becomes a highly modified ‘ pappus/ 
which appears to be, in a great number of cases, specially adapted to facili- 
tate fruit dispersal. The pappus may assume a variety of forms, such as 
the well-known parachute mechanisms of many species, the hooked bristles 
of Bidens , etc., etc. But amongst this aggressive and dominant family, the 
genus Adenostemma appears to be unique in one particular, i. e. the posses- 
sion of a sticky, glandular pappus 2 . 
It has been noted by more than one writer, that this peculiarity aids 
the plant in the dispersal of its fruits. Trimen states that the achenes of 
Adenostemma adhere to surrounding objects by their very viscid stalked 
glands (pappus) 3 ; while Hildebrand points out that in its sticky pappus 
the plant possesses an excellent means of fruit- distribution by the agency 
of animals. Fritz Muller sent him some seeds of Adenostemma, which 
unfortunately did not germinate, and so, said he, ‘ it was impossible to study 
this interesting example any further 4 / As the whole mechanism of dis- 
persal in this plant forms a good example of co-ordinated adaptation, it 
may perhaps be worth describing in some detail. 
1 See the abstract of a paper read by the author before Section K of the British Association. 
B. A. Report, Southport, 1903, p. 859. 
2 The generic name, indeed, has reference to this fact— ad-qv, a gland, and a crown : see 
Forster, Characteres Generum Plantarum, London, 1776, p. 90. 
3 Trimen, a Handbook to the Flora of Ceylon, London, 1895, vol. iii, p. 13. 
4 Hildebrand, Ueber die Verbreitungsmittel der Compositenfriichte, Bot. Zeitung, 1872, 
vol. xxx, p. 12. 
[Annals of Botany, Vol. XX. No. LXXIX. July, 1906.] 
