90 ST1PA. [CHAP. 



downwards, and so on until the proper depth was 

 obtained. A species of Anemone (A. montana) 

 again has essentially the same arrangement, though 

 belonging to a widely separated order. 



A still more remarkable instance is afforded by a 

 beautiful South European grass, Stipa pennata (Fig. 

 55), the structure of which has been described by 

 Vaucher, and more recently, as well as more com- 

 pletely, by Frank Darwin. The actual seed is small, 

 with a sharp point, and stiff, short hairs pointing 

 backwards. The upper end of the seed is pro- 

 duced 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 comes 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. 



I have already mentioned several cases in which 

 plants produce two kinds of seeds, or at least of pods, 

 the one being adapted to burying itself in the ground. 

 Heterocarpism, if I may term it so, or the power of 

 producing two kinds of reproductive bodies, is not 

 confined to these species. There is, for instance, a 

 North African species of Corydalis (C. heterocarpa of 





