852 



THE DISPERSION OF SPECIES BY MEANS OF FEUITS 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 

 sqvMmata, Megacarpcea laoiniata, Mimosa hispidula, JEschynomene glabrata, and 

 Lunaria rediviva (see figs. 467 1- ^' ", and p. 445, fig. 339 S 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 Leguminosae (e.g. Secwrida virgata and Gentrolobium robustum; 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 SilicLUOse fruit of Liinaria rediviva ; tlie two valves of the fruit have become detached ; seeds are fastened to the inside 

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

 of Heliosperma gimdrifidum after dehiscence; the seeds are being shaken out by the wind. ^A seed of Seliosperma 

 quadrijidum magnified, 6 Capsule of a Dioscorea after dehiscence, the winged seeds being blown away by the wind. 



Banisterias, belonging to the Malpighiacese (e.g. Acer Monspessulanum- 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 Umbelliferse (e.g. Opoponax Gretica and Laserpitiwm latifolium; 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- 

 pighiacese, with four wings, of which 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 Oyrocarpus, of the family 

 Combretacese, 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 becomes winged 



