160 Transactions of the Society, 



position so as to be exposed to the action of wind, as, for instance, 

 in many Composites, Trifolium stellatum, etc. In many grasses, 

 however, the awns are hygroscopic, and thus serve to move the 

 seeds, as in the so-called live oats. The awns are bent, and the 

 part below the bend is spirally twisted. The spiral closes up or 

 relaxes according to the amount of moisture in the atmosphere. 

 In Avena sterilis two glumes are awned, and the awns twist in 

 opposite directions, so as to cross and press upon one another. 

 Ultimately they part with a sudden jerk, and the whole seed gives 

 a spring. 



In other cases the unrolling awn presses against some fixed 

 body, and thus pushes the seed. 



Perhaps the most remarkable example is afforded by Stipa 

 pennata (fig. 36), a South European and doubtful British species, 

 the structure of which has been described by Yaucher, and 

 more recently, as well as more completely, by Francis Darwin. 

 The actual seed has a sharp point, and stiff, short hairs point- 

 ing backwards. The upper end of the seed is produced into a 

 fine twisted corkscrew-like rod, which is followed by a plain 

 cylindrical portion, attached at an angle to the corkscrew, and 

 ending in a long and beautiful feather, the whole being more than 

 a foot in length. The long feather, no doubt, facilitates the 

 dispersion of the seeds by wind ; eventually, however, they sink 

 to the ground, which they tend to reach, the seed being the 

 heaviest portion, point downwards. So the seed remains as long 

 as it is dry, but if a shower conies on, or when the dew falls, the 

 spiral unwinds, and if, as is most probable, the surrounding 

 herbage or any other obstacle prevents the feathers from rising, 

 the seed itself is forced down and so driven by degrees into 

 the ground. 



In the case of what we generally call fruits, such as the cherry, 

 currant, peach, etc., the seeds are imbedded in a sweet, juicy pulp. 

 In some cases the pulp only is eaten, and the seeds are rejected ; 

 in others the seeds also are swallowed, but they pass through 

 uninjured ; moreover, small birds often drop the seeds, and occa- 

 sionally fall victims to hawks, etc., or perish from other accidents, 

 so that the cases are numerous where even digestible seeds have a 

 chance of growing. Some seeds mimic small insects, and are no 

 doubt picked up, and carried some distance before the mistake is 

 discovered, by birds (see, for instance, the Mallows), or even by 

 insects, as in the case of Melampyrum. 



Some species have two kinds of seeds, one, Calendula officinalis 

 (the Mary gold of gardeners) has three ; the head comprises many 

 seeds on a flat disk, and the outer row or rows are hooked, the next 

 few bullate so as to catch the wind, while the central ones resemble 

 small caterpillars. 



Texture. — Another element to be considered is the texture of the 



