THE DISPERSION OF SEEDS AND SPORES. gS 



less importance than the power to penetrate to the 

 soil. The prevalent spindle-shape of grass-seeds is 

 well fitted for penetrating a resisting medium. 

 Many of them are boat-shaped, while the seeds of 

 Bromus steHlis and Hordeum tnurinum have the 

 exquisitely symmetrical form of a gondola. A 

 torpedo-shape is not uncommon, and the elongated 

 almost needle-like seeds of the bog asphodel {Nar- 

 thecium) have the advantage of being able to pass 

 readily between the erect leaves of the plant itself, 

 the stems of rushes, etc. In some cases the point 

 of the seed is barbed and the awn feathered, so that 

 the resemblance to an arrow is very marked. 

 Bromus steHlis seems to throw its grains from the 

 spike by hygroscopic action. Even to such javelin- 

 like seeds the wind may be of service, if not in 

 carrying them to a distance, at least in helping 

 them to force their way through matted grass to 

 the soil. The traiisjDort of an aristate grain may 

 also be indirectly brought about by the action of 

 the wind. Suppose a grain of barley to fall on a 

 waving field of its own species. If the crop is close 

 the seed will float almost as if on w^ater, and, in 

 consequence of its barbed awn, be borne along, 

 washed by waves, as it were, towards the margin 

 or thinner portions of the field. The movements 

 of the stalks, acting on the barbs of the awn when 

 it once begins to descend, will cause the seed to 

 force a passage to the soil, into which it may even 

 penetrate some little distance by the same kind of 

 action. The awns of Erodium, Anemone, Clematis, 

 etc., are useful in this way. It may therefore 

 reasonably be supposed that the awn of a grass to 

 some extent serves the same purpose. 



Comparing these elongated seeds with the broad- 

 winced samara of Acer, we are reminded of a 

 corresponding distinction in the animal kingdom. 

 The body of a bird is, in general, short, but its 

 expanded wings give great breadth. This shape is 

 convenient enough for a creature which moves 



