312 Yapp . — Fruit-d ispersa l in Adenostemma viscosum. 
My own attention was first called to this method of fruit-dispersal in 
Adenostemma viscosum, Forst., during a visit to the Malay Peninsula 1 in 
the year 1899, by finding one day a few of its fruits firmly gummed to my 
legs, by means of some short, sticky processes. The latter are in reality 
the glandular setae (generally three in number) which in this plant repre- 
sent the pappus. These setae, or stalked glands, are situated on a projecting 
ring of tissue (the calyx ring), which crowns the inferior ovary (Fig. 4). 
At the base of each seta is a swelling, which is visible only during the 
flowering stage (p. Fig. 4). 
As in the capitula of many other Compositae, the torus, during the 
ripening of the fruits, assumes a more convex shape, while the involucral 
bracts, which are at first erect, become spreading, and finally completely 
reflexed (Figs. 1-3). Meanwhile, all the corollas of the capitulum, as well 
as the styles, are detached at their bases, and fall off en masse (Fig. 2). The 
pappus now begins (usually, in the cases observed, before the actual throw- 
ing off of the corollas) to excrete an exceedingly viscid, clear liquid, which 
forms a large drop surrounding the tip of each seta. In this condition the 
pappus setae bear a marked resemblance to the leaf * tentacles ’ of a 
Drosera. At the same time the setae gradually move from a vertical into 
a horizontal position ; and, during this process, the swellings at their bases 
(which, as will be seen later, are really pulvini) disappear. The tiny fruits 
are now fully exposed, and are ready to attach themselves to any passing 
animal (Fig. 3) 2 . 
Under a low power of the microscope, the pappus bristles have the 
appearance shown in Fig. 4, each being crowned by a number of capitate 
secretory hairs, set so closely together as to form a continuous gland. The 
capitate hairs (Fig. 5), which are of a type not uncommon in the Compositae 3 , 
extend further down the seta on its exterior than they do on the side next 
to the corolla. Similar glandular hairs, but longer and narrower than those 
of the pappus, are found on many other parts of the plant, e. g., the lower 
part of the corolla, and the pericarp wall (Fig. 4), also on the peduncles, 
leaves, &c. 
The secretion of the pappus-hairs is exceedingly sticky, and may retain 
(to a large extent) its adhesive power even after the fruits have been kept 
in a dry condition for some years. Water appears to have no effect on this 
secretion, though it readily dissolves in ether and some other solvents. It 
1 This species is widely spread throughout the tropics of both the Old and New Worlds, though 
the remaining four or five species of the genus are confined to the latter. 
2 Hoffmann figures (in Engler and Prantl's Pfianzenfamilien, Teil IV, Abt. 5, p. 132, Fig. 77, o) 
a fruiting capitulum of A. viscosum with the involucre not reflexed. This figure was probably taken 
from an immature capitulum, as in all cases, I believe, the involucre is finally reflexed. 
3 See Hanstein, Ueber die Organe des Harz- und Schleimabsonderung in den Laubknospen, 
Bot. Zeit., 186S, vol. xxvi, pp. 734 et seq., also Haberlandt, Physiologische Pflanzenanatomie, 
2nd ed., Leipzig, 1896, p. 433. 
