12 ON SEEDLINGS 



Seed large, orbicular, laterally compressed, pale brown or 

 whitish ; testa thickened, hardened, almost bony, forming a 

 strong marginal ridge all round the seed except at the hilum and 

 micropyle, and also a submarginal ridge on each face; tegmen 

 black, crustaceous, closely adhering to the testa, brownish on its 

 inner face and finely reticulate ; micropyle and hilum contiguous, 

 basal. 



Endosperm in the mature seed scanty, white, subfarinaceoup, 

 generally forming a thin layer surrounding the embryo, but thickest 

 in the angle formed by the curve of the latter and leaving an 

 evident trace there when it has all been absorbed elsewhere. 



Embryo curved or hooked, large, assuming this shape from 

 the enormous thickening of the testa, almost colourless when dry, 

 white when moist ; cotyledons subulate, linear, obtuse, entire, plano- 

 convex or semiterete, considerably narrowed to the sharply incurved 

 tip, incumbent ; radicle short, oblong, obtuse, bent nearly at right 

 angles to the cotyledons, lying close to the micropyle where the 

 testa is thinnest. 



Opuntia occidentalis, Engelm. (fig. 400). 



Hypocotyl subterranean, stout, tapering downwards, pale purple. 

 Cotyledons succulent, unequal, 

 ovate, obtuse or tipped with a carti- 

 laginous point, nearly flat above, con- 

 vex on the back ; glabrous, shining, 

 deep green, mottled with minute pale 

 grey markings ; larger one 1'85 cm. 

 long, 9 mm. wide ; shorter one 1*4 cm. 

 long, 7'5 mm. wide, persistent. 



Stem succulent, erect, glabrous, 

 deep green, shining, leafy, ultimately 

 PIG. 400. Opuntia occidentalis. naked or without leaves, and fur- 

 nished with tufts of long, slender, 



glabrous, bristly, white spines, springing from woolly cushions, in 

 numerous rows ; internodes very short, each about 2 mm. long. 



Leaves small, numerous, succulent, forming longitudinal spiral 

 rows on the stem, subulate, or narrowly conical, acute, glabrous, 

 dull green, seated on little elevations of the stem, 1-5-2-25 mm. 

 long, -5-- 75 mm. wide, deciduous. 



The seedling of Opuntia Labouretiana, ? Auct., closely resembles 

 the last, but has its unequal cotyledons wider, and the young stern 

 clavate. 



