MIMICRY. 535 



{Bignoniaced). One of the best-known forms {Calo- 

 santhes indicd) is given in the woodcut (fig. j6). The 

 membrane which surrounds the seed is beautifully- 

 delicate and transparent, and is a favourite object 

 with microscopists. This type of seed is represented 

 again in the cucumber family, in which winged seeds 

 are rare, and is, in fact, almost an imitation of the 

 seed of the Calosanthes. In our figure (fig. 76) it has 

 been reduced by about one-third, so as to bring it 

 within limits ol the page. It does not differ more 

 from the seed of one of the Bignoniaceae than these 

 seeds differ amongst themselves. In another family 

 (Apocynacece), similar winged seeds occur (as in 

 Aspidosperma excelsum from Guatemala), although it 

 is not a special feature in that family for the seeds 

 to be expanded in a membranaceous wing. 



Every schoolboy is acquainted with the downy 

 crest of the achenes, or fruits, of the dandelion and 

 thistle. This crest of delicate hairs, or pappus, is 

 common in composite plants, but it is not confined 

 to them. From the annexed woodcut (fig. 78) it will 

 be seen that one of the forms, with the crest sessile, 

 is reproduced in three other families, viz., in Sarcos- 

 temma (a) one of the Asclepiadacem, in Echites scabra, 

 one of the Apocynacem (b), in the willow herb or 

 Epilobium, one of the Onagracea (c), and in the milk 

 thistle, Silybum marianum, one of the Composites. 

 There is more difference in the character of the 



