MIMICRY. 335 



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

 santJies indicd) Is given in the woodcut (fig. ']6). 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 CalosantJics. In our figure (fig. 'jG) it has 

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

 within limits of the page. It does not differ more 

 from the seed of one of the Bignoniaceae than these 

 seeds differ amongst themselves. In another family 

 {ApocynacecB), similar winged seeds occur (as in 

 Aspidospcrma cxcelsnm 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. ']%) it will 

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

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

 iemma (a) one of the Asclepiadacece, in Echitcs scabra, 

 one of the ApocynacccB {b), in the willow herb or 

 Epilobmm, one of the OnagracecB {c), and in the milk 

 thistle, Silybnvi viarianum, one of the CoinpositcB. 

 There is more difference in the character of the 



