408 OX SEEDLINGS 



the ascending nerves prominent beneath, or three- to five-nerved 

 from the base in the lower half of the leaf ; petioles semiterete, 

 flattened or subconvex on the upper surface, gradually tapering up- 

 wards, channelled at the insertion of the lamina, densely glandular- 

 pubescent, viscid, fleshy. 



First pair small, unequal ; one obovate, the other similar but 

 wider. 



Second pair unequally developed ; large one oval, obtuse, with a 

 lamina 2*3 cm. long, 1'7 cm. wide, and a petiole 4*8 cm. long ; 

 smaller leaf rotund, concave, 9 mm. in diameter with a petiole 3 mm. 

 long. 



Ultimate leaves opposite, distichous, and all turned to the upper 

 side of the prostrate stem, developing unequally from the bud and 

 always with laminae of a different shape the one from the other, and 

 petioles of unequal length ; smaller leaves rotund, slightly cuneate 

 at the base, trinerved in the lower half and arranged alternately ; 

 larger broadly ovate, rounded at the end, less frequently broadly 

 oval, obtuse, three- to five-nerved in the lower half, and also 

 alternate. 



Abronia nmbellata, Lam. (fig. 602, B). 



Achene small, narrowly obovoid, slightly compressed on one side, 

 glabrous, shining, straw-coloured with a brown line running along 

 each side for the greater part of its length, corresponding to the cur- 

 vature of the ovule ; anthocarp five-winged with the wings broaden- 

 ing upwards and tapering cuneately to the base, glabrous ; wings 

 nerved and subreticulated transversely. 



Seed pale-coloured or white ; testa thin, membranous ; chalaza, 

 hilum and micropyle contiguous, basal ; raphe none. 



Endosperm rather copious, farinaceous, white, forming a mass 

 occupying the centre of the seed. 



Embryo as in A. arenaria. 



Seedling. 1 



Primary root very little or altogether unbranched in the early 



Hypocotyl erect or curved, or decumbent, terete, pale green or 

 pinkish, or reddish, stout, shortly glandular-pubescent, 1-1-8 cm. 

 long, produced into a footlike process at the base on one side, which 

 probably assists in keeping down the fruit while the germinating 

 embryo makes its exit. 



Cotyledons very unequal immediately and for a considerable time 

 1 Figured by Darwin in Movement of Plants, p. 95. 



