858 



THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. 



to remain poised in the air. The hairs arise either from the surface of the seed-coat 

 (testa), as in the Cotton trees (BoTnbax and Oossypium; see figs. 470 ^ and 470^), or 

 else they spring from the base of the seed, as in Poplars and Willows (Populus 

 and Salix; see p. 423, figs. 318 3 and 313 4. ^ 424^ fig. 319 and fig. 471 1°). In the 

 Bulrush (Typha; see fig. 471 *) they take their rise from the pedicels of the fruits, 

 and in several Ranunculacese (e.g. Anemone sylvestris; see fig. 470^) from the 

 achenes themselves. In other cases they arise from the floral-leaves, as, for instance, 

 in the Cotton-grass {Eriophorum; see fig. 471 % where the structure which repre- 



Fig. 472. — Dispersion of fruits and seeds by the wind. 



* Geum montanum. 



i Melica Balansce. ^ Calamagrostis Epigeios; nat. size. 3 xhe same magnified. 

 speciosus. 6 Epilohium collinum. ' Clematis Flammula. 



^Eschynanthus 



sents the perianth is transformed into delicate hairs, and in Trifolium plumosum, 

 where the fruiting calyx is wrapped in wool. In many Grasses the glumes are 

 beset with extremely fine hairs (e.g. Melica and Calamagrostis; see figs. 472 ^' 2. ^\ 

 in Micropus, of the Compositse, long hairs project from the scales of the involucre 

 and envelop the entire capitulum in a flocculent mass, and in the Venetian Sumach 

 or Wig-plant (Rhus Cotinus) the stalks of abortive flowers are covered with a 

 woolly down, which serves for the dispersion of the fruits, whose stalks are usually 

 free from wool. Lastly, we have the cases where the fruits or seeds are kept 

 suspended in the air for a more or less prolonged period by means of special hairy 

 tails. Either the seeds are tailed at both ends, as in jSschynanthus (see fig. 472 % 

 one of the Gesneracese, in which the tiny seeds are furnished with two long hairs, 

 one at each end, or else the style lengthens after the flower has faded and becomes 

 converted into a spirally-curved tail, which remains attached to one side of the 



