82 TRANSACTIONS, NATURAL HISTOKY SOCIETY OF GLASGOW. 



From the examples just given it will be seen that 

 wind-carried seeds present two well-marked types, 

 viz., the winged and those furnished with hairs. 

 The former are most characteristic of lofty trees ; 

 the latter are common on herbs and shrubs. Broad 

 wings are unobjectionable in seeds blown from a 

 height, but hairs are decidedly better when the seed 

 is launched from a low level. Wings are open to 

 the objection that when the seed is carried along 

 by the wind a short distance above the ground, the 

 expanded surface they present is almost certain to 

 encounter some obstacle, with the result that the 

 flight of the seed is arrested, and it falls to the 

 earth. For this reason winged seeds are not well- 

 adapted for low-growing plants. Another objection 

 to wings is that they prevent the seed from readily 

 reaching the soil if it happens to be covered with 

 withered grass or other vegetation. Hairs have the 

 advantage that they give the required buoyancy 

 and do not offer so much resistance to the passage 

 of the seed through among other plants. 



The power of penetration belongs in a still higher 

 degree to a third class of seeds. These are not 

 specially adapted for wind-dispersion, being com- 

 monly without either wings or hairs, but instead 

 are furnished with a long slender awn. The beard 

 of Barley, and other aristate grains, is made up of 

 such appendages. Occasionally the awn is hygrosco- 

 pic ; but in most cases it is rigid, brittle, and scabrid 

 on its edges. Its minute barbs are directed towards 

 the apex, so that when the finger is drawn along 

 the edge of the awn from the apex towards the 

 base it is felt to be rough. If a grain of barley be 

 placed in one's sleeve, the movements of the arm 

 will cause the seed gradually to work its way up- 

 wards towards the shoulder. Or again, if the seed 

 be gently shaken in a blanket it will move along in 

 one direction only, as the scabrid bristle prevents 

 any backward movement. In the dispersion of grass- 

 seeds transport to a distance would seem to be of 



