PHANEROGAMIA : FLOWERS. 



419 



(fig. 255.), with a strikingly developed radical extremity (fig. 255. a.), and 

 the embryo of Scheuchzeria (fig. 256.), with a predominantly developed 

 cotyledon (fig. 256, b.\ appear best fitted. If the radicle is destined to 

 be little or not at all developed subsequently in germination, there are 

 formed already at this period, from the place where the cotyledon is 

 connected with the bud (as the first node of the plant), adventitious 

 roots, which, in the embryonal condition, still remain inside the paren- 

 chyma of the true root (fig. 257, b d.), as in Lemna, Pistia, Graminece, 



256 



257 



260 



ScitaminecB. The vaginal portion of the cotyledon may likewise be- 

 come more or less developed, and wholly, partly, or not at all enclose the 

 terminal bud : in the first case, the borders of the sheath always become 

 blended, so as to leave only a large (Aracetz, 257. A. c. B. c.) or small 

 (Liliacece) slit, which, however, is, in all instances, still perceptible on 

 the ripe embryo ; in the second case, the bud partly projects out from 

 the slit, e. g., Scheuchzeria, some species of Pothos, &c.; the last .case, 

 which is the rarest, occurs in Stratiotcs, Aponogeton (fig. 258, c.), 

 Ouviranda, Orontium aquati- 

 cum, &c. The forms of these 258 

 individual parts are also very 

 various, as in general the or- 

 gans of plants are not bound 

 down to any particular form. 

 Sometimes the cotyledons are 

 developed broad, obconical, on 

 the little conical papilla, e. g., 

 Pothos reflexa (fig. 260.), 

 sometimes umbrella-shaped, or 

 like an Agaric-pileus, as in the 

 Cyperacece (fig. 259.) ; some- 

 times even like a hollow cup, 



856 Scheuchzeria palustris. A, Longitudinal section of the embryo : a, radicle ; 



b, cotyledon ; c, slit of the same, with the plumule. 



257 Pistia obovata. A, Embryo : a, radicle ; 6, cotyledon ; c, slit of the same. 

 B, Longitudinal section of the embryo : a, b, as in A ; c, slit of the cotyledon, with the 

 very simple plumule ; d, adventitious root. 



858 Aponogeton distachyon. Embryo, a, Radicle ; b, cotyledon ; r, free plumule. 



259 Isolepis supina. Longitudinal section of an embryo, , Radicle ; 6. cotyledon ; 

 r, plumule covered by a sheath from cotyledon, and directed downward. 



860 Pothos reflexa. Longitudinal section of an embryo, a, Radicle ; I, cotyledon ; 



c, its slit, with the plumule ; .r, doubtful second bud. 



r. E 2 



