48 On the Aihu, CeratopkyUacoa* 



the microjn le. The correctness of this view is demonstrated 

 hv a consideration of their internal structure. The embryo, 

 enclosed in a peculiar covering (the thickened and persistent 

 membrane of the nucule) lies in immediate contact with the 

 (organic as well as geometrical) base of the seed, the residue 

 • »t* the cavity being fdlcd with a rather firm albumen; the radi- 

 cular extremity pointing from the, hihnu and towards the distant 

 micropyle. The of Cabombaceee are therefore suspended 



and orthotrogpus, as in Ceratophyllacftse. The principal dif- 

 uce between the two orders, bo far as respects the structure 

 of the ovule and seed, consists, therefore, in the h >s developed 

 embryo of the former being wholly enclosed in the persistent 

 sac of the nucule (as in Nymphseacese), and in the presence of 

 albumen. It is evident, therefore, that the order Ceratophylla- 

 ceae is almost as closely allied to Cabombacete as to Nelum- 

 biace.e, and that it should stand in the immediate vicinity of 

 these two orders, notwithstanding the much lower develope- 

 ment of its flora] organs, and other diversities attributable to its 

 wholly submersed habit. 



As to the affinity of the order Cabombacese with Nelumbiacese 

 and Nymphaeaceae, it ma\ be remarked that it agrees with 

 the former in its innate anthers, apocarpous ovaries, and nearly 

 solitary orthotropous seeds ; and with the latter in the presence 

 tlbumen, and of a sac enclosing the embryo. It differs 

 from Nelumbiacese chiefly in the albuminous seeds, and less 

 developed embryo, and in the absence of an enlarged torus; 

 while Nymphaeacese, bow< v< r close the alliance, are essentially 

 distinguished from both thi se families b\ their adnate anthers, 

 polj spermous and s_\ acarpous 01 aries, and analroyous seeds.* 



• In both Nympbi and Cabombaceae me embryo is commonly 



i mated nearly without ilie albumen, at the base of thr 



. this important diffi that in the latter the 



ed a) th< true base of the seed, i. e* dbxt th< chalaza; 



win'' Pap reracete, ice.) il !•■ «imated at the ex- 



