Urticales.] 



CERATOPHYLLACE^.. 



263 



Order LXXXV. CERATOPHYLLACE^E.— Hornworts. 



CeratophyUeae, Gray's Arrangement of Brit. Fl. 2. 554.; DC. Prodr. 3. 73. (1828); Asa Gray, Ann. 



Lye. N. York, 4. 48. (1837) ; Schleiden in Linncea, 11. 540. (1837) ; Endl. Gen. Ixxxiii. 

 Diagnosis. — Urtical stcbmersed Exogens, with an inferior radicle, an exalhuniinous 

 embryo, and a large many-leaved plumtde. 

 Submersed herbs, with dichotomous, cellular, verticillate leaves. Flowers monoecious. 

 Calyx inferior, many-parted. ^ Stamens from 12 to 20 ; filaments wanting ; 

 anthers 2-celled. $ Ovary superior, 1 -celled ; ovule soUtary, 

 I'll^Wl^, pendulous, orthotropal ; style pervious ; stigma fihform, oblique. 



- ' Nut 1-seeded, indeliiscent, terminated by the hardened stigma. 



Seed pendulous, solitary ; albumen ; embryo with 2 cotyledons ; 

 plumule many-leaved ; radicle inferior. 

 j It would be difficult to name a plant concerning whose affinity 



more different opinions have been entertained. Possessed of the most 

 simple organisation, it scarcely presents a single salient point for con- 

 sideration, with the exception of its plumule being very highly 

 developed. The number of cotyledons, although only two, as 

 Schleiden has shown, appears to be four ; and, m consequence of 

 this, Richard placed it near Conifers, with which it seems to me to 

 have no kind of affinity. Nevertheless, Schleiden leans towards 

 Richard's view ; in order to support which, he calls the male flower 

 an amentmn. De Candolle urges its relation to Hippuris and Myrio- 

 phyllum, among Hippurids, from which it differs in its superior 

 ovary ; and he inquires whether Naias, wliich, according to some, is 

 dicotyledonous, does not belong to the same Order. Agardh actually 

 places it among Naiads. 



I formerly suggested the possibihty of its beuag a degeneration of 

 Nettleworts, and as bearing the same 

 relation to them as ISIossweeds and 

 Starworts to some unknown Order, 

 or as Lemnads to Arads. This opinion 

 Schleiden has criticised with uaci^-ility, 

 forgettmg that it was formed upon the 

 assumption that the radicle of Cerato- 

 phyllum is superior, an error of De 

 Candolle's, of which I was not then aware. 

 And even now, I do not see where it can 

 be better placed, unless near Chenopods. 

 It agrees with the Urtical Alliance in 

 ha\Tng incomplete, unisexual flowers, a 

 free ovary consisting of a single cai'pel 

 and a sohtary ovule ; but it differs in 

 having the radicle inferior, and no albu- 

 men. The high development of the 

 Fig. CLXXVIII. plumule may however, in this mstance, 



as in Waterbeans, (NelumbiaceEe), be a compensation for the want of albumen, 

 enabhng the embryo to germinate without assistance, as soon as it is exposed to tne 



^^^nTrnworts'may also be compared with Chenopods, on account of then- incomplete 

 flowers, inferior radicle, simple free carpel, and single oviile ; and the unisexual flox^ ers 

 and want of albumen would not be opposed to such a comparison. But the "^isexuality 

 of Chenopods is the exception, not the rule, and the ^traightness of the embryo of 

 Ceratophyllum is as much at variance with the characteristic mark of that Order, as its 



Fig. CLXXVIII. — Ceratophyllum submersum. — 1. c? flower: 

 section of ovary, the style being cut off; 4. fruit ; 5. embrjo. 



2. ? ditto ; 3. perpendicular 



