(518 COTYLEDONS. 



on the other are made to stand off somewhat; these latter press against the 

 particles of earth above them, and act as levers, by means of which the whole 

 fruit at the moment of bending in the given direction becomes pressed down 

 deeper into the ground. This action is continued every time the fruit wobbles 

 from side to side, so that bit by bit it is buried. The only question is, how these 

 sudden alterations in position of the fruit fixed in the ground can be brought 

 about. A glance at fig. 147 shows that every wind, even though slight, which 

 strikes the long feathery portion of the awn, must immediately be followed by 

 an alteration in the position of the fruit. Just as a weather-cock on the top of 

 a roof in a strong east wind does not point invariably towards the east, but 

 generally makes short veerings to the north and south, so the plumed awns 

 fluttering to and fro in the east wind swerve momentarily towards the north and 

 south, and this change of direction causes the fruit sticking in the soil to incline 

 to various sides. When the wind veers round of course an alteration occurs in the 

 direction of the feathery awn, and consequently a more strongly-marked inclination 

 of the fruit occurs, so that a see-sawing motion of the latter will be unavoidable. 

 The wind, therefore, is an important factor in driving the fruit into the ground. 

 The awns of the Feather-grass, however, have two other peculiar contrivances, 

 viz., below the feathery portion they are bent twice like a knee, and they are 

 also spirally twisted like a corkscrew. This bent and twisted part of the awn is 

 exceedingly hygroscopic; in rainy weather the knee-shaped bend almost entirely 

 disappears; the awn bristles and straightens itself, the spiral unwinds in damp 

 weather, and twists up again in dry air. These movements are evidently conveyed 

 to the glume, and produce alterations in its inclination, which again cause an 

 advancement of the tip into deeper layers of earth. 



These movements of the lower portion of the awn produced by the varying 

 humidity of the air make themselves specially felt when the upper portion has in 

 some way become entangled with the stems and leaves of the other steppe-plants, as 

 frequently happens. When in dry weather the fruits of the Feather-grass become 

 detached and are blown by the wind over the steppes, it is almost unavoidable 

 that they should remain fastened by their knee-like bent portion to haulms, stems, 

 and the like that the feathery part should be hemmed in between two neighbour- 

 ing stems of other plants, or occasionally even entangled with them (cf. fig. 147 2 ). 



But as soon as the upper portion of the awn is fixed, and later on in damp 

 weather the lower knee-shaped portion of the same awn has become straightened 

 and the spiral twists uncoiled, the fruit is necessarily forced into the ground with 

 a twisting movement, and is also pressed now to this side and now to that by the 

 unequal straightening of the knee-shaped bend. Any backward movement of the 

 fruit from a subsequent drying up of the awn is prevented by the above-named 

 stiff hairs, in the manner already described. It is much more likely that one of 

 the stems to which the awn has attached itself should be somewhat bent by this 

 contraction of the awn, than that the glume already driven a certain depth into 

 the ground and there anchored should be drawn out. 



