870 



THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. 



phenomenon in question is not merely a matter of conjecture, but has come actuallj^ 

 under observation. 



About 10 per cent of all Flowering Plants possess fruits or seeds which are 

 dispersed by means of clawed or barbed processes. This mode of dissemination is 

 very like that whereby sticky fruits attain the same object. The part of the plant 

 which is provided with these structures hooks on to the hairs, bristles, or feathers 

 of any bird or other animal that happens to come into contact with it. The conse- 

 quence is that it is torn away and carried off by the animal. This act of depredation 

 is of course not intentional on the part of the creature that performs it; on the 

 contrary, such appendages are a source of discomfort, and are got rid of as soon as 



Fig. 476.— Sticky fruits. 



I Salvia glutinosa. 2 Stalked adhesive glands on the fruiting calyx of the same; x60. « Plv.mbago Capensis. * Pisonia 

 aculeata. ^ stalked adhesive glands on the fruit of the same ; x60. ^ Linnceaborealis. f Fruit of the same ; x5. 



possible. But in many cases this is not accomplished until a considerable distance 

 has been traversed, and sometimes the troublesome objects remain for weeks in the 

 creature's coat or mane. The organs of attachment are either hooked at the tip or 

 beset with barbs (see figs. 477 ^ and 477 ^^). In the latter case the barbs are borne 

 on special rigid bristles or needles, and are either collected together at the top, as in 

 a harpoon, or else are arranged in longitudinal rows as in a hackle for combing flax. 

 Only in a few instances {e.g. in Poly gala glochidiata, Stellaria glochidiata, and 

 Lii7inanthemum nymijhceoides) do these structures, which may be classed together 

 as hooked bristles and hooked prickles, occur on the seeds themselves; usually they 

 are appendages of the pericarp, and as such exhibit every degree of size possible, 

 from the delicate, hooked bristles on the small nutlets of the Enchanter's Nightshade 

 (Circcea, see figs. 477 ^ and 477 ^) to the thick, firm claws on the fruits of the African 

 Harpoon Fruit (Harpagophytum procumbens). The hooked spines of the latter 

 fruits attain to the size of crows' feet, and are a notorious source of vexation to 



