852 



THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. 



according to the particular plant considered, are in the form of scales and leaflets 

 which become detached separately. Instances of this kind are afforded by Artedia 

 squamata, Megacarpcea laciniata, Mimosa hispidida, ^schynomene glabrata, and 

 Lunaria rediviva (see figs. 467 i' °' i\ and p. 445, fig. 339 ^ and fig. 466 ^). 



With these forms may be classed also such fruits and seeds as are furnished 

 with wing-shaped appendages. The wings are either produced from the seed-coat, 

 as in Pines and Firs (see p. 441, fig. 335 '"), or else arise from the carpels. A single 

 wing, which stands out to one side, is developed in the case of the pods of some 

 tropical Leguminosse (e.g. Securida virgata and Centrolobium rohustum; see p. 445, 

 fig. 339 ^), and in the separate parts of the double fruit of the Maple and of the 



Fig. 466. — Dispersion of fruits and seeds by the wind. 



1 Siliquose fruit of Lunaria rediviva ; the two valves of the fruit have become detached ; seeds are fastened to the inside 

 of eacli valve. 2 Opened capsule of a Bignonia from which winged seeds are being carried off by the wind, s Capsule 

 of Heliosx>erma giiadrifidum after dehiscence; the seeds are being shaken out by the wind. *A seed of Heliosperma 

 quadrifidum magnified, s Capsule of a Dioscorea after dehiscence, the winged seeds being blown away by the wind. 



Banisterias, belonging to the Malpighiaceae (e.g. Acer MonspessulanivTn and 

 Banisteria Sinemariensis] see figs. 467'' and 467-^°). The achenes of Birches 

 and of the Tree of Heaven (e.g. Betula verrucosa and Ailanthus glandulosa; see 

 figs. 467 ^ and 467 ^^) bear two laterally placed wings in each case. The mericarps 

 of many Umbelliferae (e.g. Opoponax Cretica and Laserpitium loMfolium; see 

 figs. 467^ and 467^^) have wings projecting from the back; the fruits of some 

 Polygonums (e.g. Polygonum dumetorum and P. Sieboldi; see fig, 467^) are 

 furnished with three wings, and those of Triopteris bifurca, one of the Mal- 

 pighiaceae, with four wings, of wliich two are large and two small (fig. 467 ^). In 

 other cases some of the floral - leaves are transformed into wings for the fruit, 

 as, for instance, in Dryobalanops, of the family Dipterocarpese, in which five sepals 

 are in the form of long wings (see fig. 468 ^), and in Gyrocarpus, of the family 

 Combretaceae, in which two of the 4-7 unequal segments of the calyx are similarly 

 adapted (see fig. 467 ^). It is of common occurrence for the fruits to become winged 



