356 THE POPULAR SCIENCE MONTHLY. 



horse-chestnut, beech, Spanish chestnut, walnut, etc. That these seeds 

 are used as food by squirrels and other animals is, however, by no 

 means necessarily an evil to the plant, for the result is that they are 

 often carried some distance and then dropped, or stored up and for- 

 gotten, so that in this way they get carried away from the parent tree. 



In another class of instances animals, unconsciously or unwillingly, 

 serve in the dispersion of seeds. These cases may be divided into two 

 classes, those in which the fruits are provided with hooks, and those in 

 which they are sticky. To the first class belong, among our common 

 English plants, the burdock {Lappa^ Fig. 14 c^), agrimony i^Agrimo- 

 nia, Fig. 14 h) ; the bur parsley ( CaucaliSy Fig. 14 c) ; enchanter's 

 nightshade {Circcea, Fig. 14 d) \ goose-grass or cleavers {Galium, 

 Fig. 14 e), and some of the forget-me-nots {3fi/osotis, Fig. 14 f). 

 The hooks, moreover, are so arranged as to promote the removal of 

 the fruits. In all these species the hooks, though beautifully formed, 

 are small ; but in some foreign species they become truly formidable. 

 Two of the most remarkable are represented on page 357 3farty7iia 

 jwohoscidea (Fig. 15 V) and IIarpagop)hyton prociirahens (Fig. 15 ci). 

 Martjmia is a plant of Louisiana, and if its fruits once get hold of an 

 animal it is most difficult to remove them. Harpagophytum is a South 

 African genus. The fruits are most formidable, and are said some- 

 times even to kill lions. They roll about over the dry plains, and, if 

 they attach themselves to the skin, the wretched animal tries to tear 

 them out, and sometimes getting them into .his mouth perishes miser- 

 ably. 



The cases in which the diffusion of fruits and seeds is affected by 

 their being sticky are less numerous, and we have no well-marked in- 

 stance among our native plants. The common plumbago of South 

 Europe is a case which many of you no doubt have observed. Other 

 genera with the same mode of dispersion are Pittosporum, Pisoniay 

 Boerhavia Slegesbeckia, Grbidelia, Drymaria, etc. There are com- 

 paratively few cases in which the same plant uses more than one of 

 these modes of promoting the dispersion of its seeds, still there are 

 some such instances. Thus in the common burdock the seeds have 

 a pappus, while the whole flower-head is provided with hooks which 

 readily attach themselves to any passing animal. Asterothrix, as Hil- 

 debrand has pointed out, has three provisions for dispersion ; it has a 

 hollow appendage, a pappus, and a rough surface. 



But perhaps it will be said that I have picked out special cases ; 

 that others could have been selected, which would not bear out, or 

 perhaps Avould even negative, the inferences which have been indi- 

 cated ; that I have put the cart before the horse ; that tlie ash-fruit 

 has not a wing in order that it may be carried by the wind, or the 

 burdock hooks that the heads may be transported by animals, but 

 that, happening to have wings and hooks, these seeds are thus trans- 

 ported. Kow, doubtless there are many points connected with seeds 



