THE DISPERSION OF SEEDS AND SPOKES. 75 



scale adherent to the seed. A scale of the inner 

 pericarp adheres in the same way to the seed 

 of the Dutchman's-pipe {Aristolochia Sipho). This 

 curious seed has, besides, a wing of its own and a 

 spongy body attached to it, but the meaning of this 

 complicated apparatus requires further investigation. 

 Winged fruits are of more frequent occurrence than 

 winged seeds. Sometimes the wing is vertical, as in 

 Peltaria, Isatis tinctoria, Anemone narcissiflora, and 

 Oxyria; or it may be horizontal, as in Paliurus 

 australis. Familiar examples of winged fruits or 

 mericarps are afforded by Acer, Ulmus, Betula, 

 Fraxinus, Thlaspi, Lepidium, Tberis, Heracleum, 

 Peucedanum, etc. Three wings occur on the fruit 

 of Thalictrum aquilegifolium, Tripteris, and on 

 several species of PolygonuTU and Begonia. The 

 appendages are still more numerous in some fruits, 

 particularly in those of the Malpighiacece, while 

 Eryngium has its fruit covered with wing-scales. 

 Occasionally — as in Ar^neria, Valerianella discoidea, 

 Salvia aursa, Polygala virgata, and Trifolium fragi- 

 ferum — the persistent calyx, more or less inflated, is 

 made to do the duty of wings. Rurnex may be 

 included here, its wings being derived from the 

 perianth. In one or two cases the pericarp or calyx 

 acquires a spongy texture, as in Margyricarpus 

 setosus. The bracts in Carpinus, Tilia, Humulus, 

 Briza, Holcus, Phalaris, etc., discharge the function 

 of wings, while a five-winged parachute is formed 

 by the persistent corolla of Melanorrhcea usitata. 



In all the cases now cited, these wing-like appen- 

 dages have a thin, membranous, or even papery 

 character, and are attached to bodies which, since 

 they separate from the mother-plant, must be 

 intended for transmission by the wind. Begonia, 

 however, has a winged, many-seeded capsule, which 

 does not detach itself from the stalk. Wings in 

 such circumstances cannot subserve flight, but present 

 a large resisting surface to the wind, so that the 

 capsule has its seeds shaken out, with the further 



