32 



ON SEEDLINGS 



curved, and the cotyledons being thick and fleshy, the inner 

 one is naturally smaller than the outer. 



In Abronia umbellata (fig. 64, B) the embryo is large, much 

 curved or doubled on itself, and lies outside the endosperm, 

 the two edges of the cotyledon reaching almost to the radicle. 

 The second cotyledon (ic) is minute, generally not more than 

 one-seventh the length of the outer one, though in one seed 

 it attained nearly half the length of the other. In another 

 species of the same genus, A. arenaria, the smaller cotyledon 

 is reduced to a mere knob (fig. 64, A, ic). 



FIG. 65. Petiveria octandra. A, seedling, half nat. size. B, embryo partly unfolded 

 x 6. C, outer and shorter cotyledon. D, inner and longer cotyledon. 



Cases in which one of the cotyledons is rudimentary also 

 occur hi the genera Eanunculus, 1 Carum, 2 Cyclamen, &c. 



In Petiveria octandra (fig. 65, A) the cotyledons are very 

 interesting. The one is about 3 cm. long, 1 broad, oblong, 

 tapering at both ends, and entire. The other is shorter and 

 broader, 2 cm. long by If broad, subcordate, with a large 

 terminal lobe, and one, more or less pronounced, on each 

 side. At first I thought this curious want of symmetry must 



1 See Irmisch, Beit, sur vergl. Marphol. der Pflanzen (Halle, 1854). 



2 Hegelmaier, Vergl. Untersuchungen (Stuttgart, 1878). 



