432 



STRUCTURE OF WINGS OF SEEDS. 



This structure is extremely well seen in the Seed of the Eccre- 

 mocarpm scaler, a half-hardy climbing plant now common in our 

 gardens ; and when its membranous ' Wing ' is examined under a 

 sufficient magnifying power, it is found to be formed by an extra- 

 ordinary elongation of the cells of the seed-coat at the margin of 





Seeds, as seen under a low magnifying power : — A, Poppy; 

 b, Auiaranthus (Prince's feather); c, Antirrhinum magus (Snap- 

 dragon) ; d, Caryophyllum (Clove-pink) ; e, Bignonia. 



the seed, the side-walls of which cells (those, namely, which lie in 

 contact with one another) are thickened so as to form radiating 

 ribs for the support of the wing, whilst the front and back walls 

 (which constitute its membranous surface) retain their original 

 transparence, being marked only with an indication of spiral 

 deposit in their interior. In the seed of Dictyoloma Peruviana, 

 besides the principal Wing prolonged from the edge of the seed- 

 coat, there is a series of successively smaller wings, whose margins 

 form concentric rings over either surface of the seed; and all these 

 wings are formed of radiating fibres only, composed, as in the 

 preceding case, of the thickened walls of adjacent cells ; the 

 intervening membrane, originally formed by the front and back 

 walls of these cells, having disappeared, apparently in consequence 

 of being unsupported by any secondary deposit.* Several other 



* See Brady in " Transactions of Microsc. Society," N.S., Vol. ix. (1861), 

 p. 65. 



