CHAP. II. EMBRYO. 217 



" Thus in Sea-wrack (Zostera marina) of which the embryo 

 is an oblong almond-shaped body with a cleft on one side, in 

 the cavity of which a long flexuose process is placed, the latter 

 is the plumule, and the former at one end the cotyledon, and 

 the radicle at the other; in Ruppia maritima, whose embryo 

 is an oblong body, cut suddenly off at one end, on which a 

 sort of curved horn crouches, the latter is the plumule, and 

 the former chiefly cotyledon; and so in frog-bit (Hydrocharis 

 morsus ranse), the embryo of which is an oblong fleshy kernel 

 with a hole on one side, in which there lies a short cylinder ; 

 the latter is the plumule, and the former the cotyledon." 



The AcoTYLEDONOUS embryo is not exactly, as its name 

 seems to indicate, an embryo without cotyledons; for, in that 

 case, Cuscuta would be acotyledonous. On the contrary, it 

 is an embryo, which does not germinate from two fixed in- 

 variable points, namely the plumule and the radicle, but in- 

 differently from any point of the surface ; as in some of the 

 Arum tribe, and in all flowerless plants. See Molil^ Bemer- 

 kimgen iiher die Eyitwicklung unci den Bau der Sporen der Cryjpto- 

 gamischen Gewdchse. Regensh. 1833. 



For further illustrations of the embryo, consult Plate VI. 

 and the explanation of its figures. 



The direction of the embryo is either absolute or relative. 

 Its absolute direction is that which it has independently of the 

 parts that surround it. In this respect it varies much in dif- 

 ferent genera ; it is either straight (Plate VI. fig. 5.), arcuate 

 (fig. 9.), or falcate, uncinate, or coiled up (fig. 8.) {cyclical)^ 

 folded up, spiral (fig. 19.), or bent at right angles (Plate V. 

 fig. 28.) {gromonical, Link), serpentine, or in figure like the 

 letter S (sigmoid). 



Its relative position is determined by the relation it bears 

 to the chalaza and micropyle of the seed ; or, in other words, 

 upon the relation that the integuments, the raphe, chalaza, 

 hilum, micropyle, and radicle bear to each other. If the sacs 

 of the ovule are in no degree inverted, but have their com- 

 mon point of origin at the hilum, there being (necessarily) 

 neither raphe nor chalaza visible, the radicle will in that case 

 be at the extremity of the seed most remote from the hilum, 

 and the embryo inverted with respect to the seed, as in Cistus, 



