392 ON SEEDLINGS 



The varieties of this species, namely P. m. intermedia and 

 P. m. asiatica, conform to the type. 



Other species have the cotyledons with their edges to 

 the axis, or placenta of the fruit, as for instance P. lan- 

 ceolata (fig. 600). The ovary is two-celled and four-ovuled, 

 but the fruit bears only one perfect seed in each cell. The 

 seed is comparatively large, occupies the whole of the cell, and 

 is oblong, peltate and deeply concave on the ventral face. The 

 embryo is nearly as long as the endosperm and straight. 

 The cotyledons are linear, semiterete in transverse section, 

 lying in the narrow way of the seed ; they almost equal the 

 endosperm in thickness, and have their edges to the placenta. 

 The radicle is shorter and narrower. The object of this 

 arrangement of the cotyledons seems to be for the greater 

 convenience of exit from the seed during germination, be- 

 cause if they had been placed in the broader plane of the 

 seed they might become too wide or even be curved in con- 

 formity with the incurving of the sides of the same, when it 

 would be impossible for them to get out. In P. media, for 

 instance, where the seeds are nearly flat, the latter do not 

 split open during germination, but the embryo escapes by an 

 opening at one end. In P. stricta it closely resembles that 

 of P. lanceolata. The fruit of P. Cynops is two-celled with 

 one seed in each cell. The seed is ovate, peltate, concave on 

 the ventral face, and has a large suborbicular hilum below 

 the middle of that aspect. The cotyledons are thicker than 

 wide, but their arrangement is precisely that of P. lanceolata. 

 The seeds of P. arenaria are also solitary in each cell and 

 agree with those of P. Cynops in every respect. 



Some species whose cotyledons lie in the narrow plane of 

 the seed differ in certain respects from those above mentioned. 

 The seed is not concave on the ventral aspect, but may either 

 be biconvex or plano-convex, and the embryo is relatively very 

 large. P. Coronopus is an instance of the former. The 

 seed is broadly oblong with a small hilum below the middle 

 of the ventral face, and is elliptic in transverse section. The 

 cotyledons are linear, as thick as they are wide, and more 

 than semiterete in transverse section, conforming pretty 

 closely to the outline of the seed. The radicle is short 



