366 



THE POPULAR SCIENCE MONTHLY 



A still more remarkable instance is afforded by a beautiful South 

 European grass, IStlpa pennata (Fig. 21), 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 backward. The posterior 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 seeds being the heaviest portion, 

 point downward^ 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 pre- 

 vents 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 bury- 

 ing itself in the ground. Heterocarpism, if I may term it so, or the 

 power of j^roducing two kinds of reproductive bodies, is not confined 



to these species. There is, for instance, a 

 North African species of corydalis ( C. hete- 

 rocarpa of Durieu) which produces two kinds 

 of seed (Fig. 22), one somewhat flattened, 

 short, and broad, with rounded angles ; the 

 other elongated, hooked, and shaped like a 

 shepherd's crook with a thickened staff. In 

 this case the hook in the latter form perhaps 

 serves for dispersion. 



Our common Thrincia Mrta (Fig. 13, h) 

 also possesses, besides the fruits w^ith the well- 

 known feathery crown, others which are des- 

 titute of such a provision, and which probably, 

 therefore, are intended to take root at home. 

 Mr. Drummond, in the volume of " Hook- 

 er's Journal of Botany " for 1842, has described a species of Alisinacece 

 which has two sorts of seed-vessels ; the one produced from large, float- 

 ing flowers, the other at the end of short, submerged stalks. lie does 

 not, however, describe either the seeds or seed-vessels in detail. 



Before concluding, I will say a few words as to the very curious 

 forms presented by certain seeds and fruits. The pods of Lotus, for 

 instance, quaintly resemble a bird's foot, even to the toes ; whence the 

 specific name of one species, Omit/wpodloides ; those of Ilippocrepis 

 remind one of a horseshoe ; those of Trapa bicornis have an absurd re- 

 semblance to the skeleton of a bull's head. These likenesses appear to 

 be accidental, but there are some which probably are of use to the 



Natural Size. 



Fig. 22. Seeds op Couvdalis 

 heteuocarpa. 



