284 



CALLITRICHACEiE. 



[Diclinous Exogens. 



Order XCII. CALLITRICHACE^.— Starworts. 



CaUitrichineae, Link. Enum. 1. 7. (1821) ; Lavklle in Ann. Soc. Linn. Par. p. 229 ; DC. Prodr. 3. 71 ; 

 Ed.pr. (1836); Endl. lxxxiv. ; Meisn.p. 336. 



Diagnosis. — Euphorbial aquatic Exogens, with definite suspended anatropal ovules, and 



a superior radicle. 



Small aquatic herbaceous plants, with opposite, simple, entire leaves. Flowers axil- 

 lary, solitary, very minute. Flowers unisexual, monoecious, naked, with 2 fistular coloured 

 bracts. <J Stamen hypogynous, single, rarely 2 ; filament filiform, furrowed along the 

 middle ; anther reniform, 1-celled, 2-valved ; the valves opening fore and aft. <j? Ovary 

 solitary, 4-cornered, 4-celled ; ovules solitary, attached to the axis, 

 suspended, amphitropal ; styles 2, right and left, subulate ; stigmas 

 simple points. Fruit 4-celled, 4-seeded, indehiscent Seeds peltate ; 

 embryo inverted in the axis of fleshy albumen ; radicle very long, 

 curved, superior ; cotyledons very short. 



I have formerly remarked, that " the affi- 

 nity of this Order to other dicotyledons ap- 

 pears to be of the same nature as that borne 

 by Lemna to Monocotyledons : they each ex- 

 hibit the lowest degree of organisation known 

 in their respective classes." Brown considers 

 the Order allied to Hippurids : an opinion in 

 which Botanists seem disposed to concur. The 

 great objection to it is this ; Hippurids are a 

 reduced form of the exalbuminous Onagrads, 

 with the petals often absent, and the calyx 

 sometimes diminished to what seems a mere 

 rim ; but in reality, in consequence of the 

 ovary being adherent, the whole of the tube 



of the calyx as well as its rim remains adhering to the ovary, so that the calyx is not in 

 fact materially diminished ; but Starworts are absolutely destitute of a calyx and 

 are albuminous. These circumstances, and the unisexual flowers of the Order, seem to 

 point to a widely different station, and accordingly, in the last edition of this work, it 

 was arranged among the Incomplete Orders- — in the neighbourhood of Mossweeds. 

 It must, however, be confessed that its relation to these plants is one of analogy rather 

 than of affinity. Nevertheless, Endlicher places it in the same situation, remarking, 

 however, that it is perhaps an aquatic form of Spurgeworts. And in this he seems to 

 be right ; at all events it differs so little from that Order, except in its indehiscent fruit 

 and amphitropal ovules, that unless we should hereafter be able to employ internal struc- 

 ture for high systematical divisions, it is in the Euphorbial Alliance that this plant will 

 remain. It is doubtful indeed whether it ought, in the present state of our knowledge, 

 to be regarded as an independent Order. 



Natives of still waters in Europe and North America. 



The uses are unknown. 



GENUS. 

 Callitriche, L. 



Numbers. Gen. 1. Sp. 6. 



Ceratophyllaccw ? 

 Position. — Euphorbiacete. — Callitrichace^;.- 



Haloragece. 





Fig. CXCVI. 



Fig CXCVI. -Callitriche verna 1. a ^ flower; 2. a J ; 3. a perpendicular section of the ripe fruit. 



