Arum.] LXXVI. AROIDE^. 421 



obliquely campanulate, tapering to a point at the top, the convolute 

 part contracted above the base. Spike half concealed in the spatha, 

 the club-shaped yellow or purplish top alone appearing above the con- 

 volute part. Berries bright red, in a short spike, on a naked peduncle, 

 the leaves and spatha having died away before they are ripe. 



In woods and thickets, under hedges, &c, chiefly in central Europe, 

 from northern Italy and Spain to southern Scandinavia. Frequent in 

 England and Ireland, doubtfully wild in Scotland. Ft. spring. [The 

 closely allied A. italicum, Miller, which occurs in several places on the 

 south coast of England, differs in its greater size, longer spathe, yellow 

 spadix, larger berries, and in the leaves appearing in winter.] 



II. ACORUS. ACORUS. 



A single species, distinguished as a genus by the leaf -like spatha not 

 enclosing the spike, and by the numerous hermaphrodite flowers con- 

 sisting of a perianth of 6 short scales, 6 stamens, and a 2- or 3 -celled 

 ovary, all closely packed in a dense, cylindrical spike. 



2. A. Calamus, Linn. (fig. 945)- Sweet Flag, Sweet Sedge. — A highly 

 aromatic, reed-like plant, with a thick, shortly creeping rootstock. 

 Leaves linear and erect, 2 or 3 feet long, about half an inch broad. 

 Flowering-stems simple and erect, the long, linear, leaf-like spatha 

 forming a flattened continuation, with the spike sessile at its base so 

 as to appear lateral ; it is cylindrical, very dense, 2 to 3 inches long, of 

 a yellowish-green colour. 



On the edges of lakes and streams, all over the north temperate zone. 

 In Britain, believed to be indigenous only in some of the eastern counties 

 of England, but has been introduced elsewhere, and in Ireland and 

 Scotland. Fl. summer. 



LXXVII. LEMNACEJE. THE DUCKWEED FAMILY. 

 A single genus, united by some with Aroidece, but anoma- 

 lous in its mode of vegetation and very reduced flowers. 



I. LEMNA. DUCKWEED. 



Floating plants, without distinct stems or real leaves, but consisting 

 of small, leaf -like fronds, either separate or cohering two or three 

 together by their edges, emitting in most species one or more fibres 

 from their under surface into the water, and multiplying by similar 

 fronds growing out of their edges. Flowers very rare, appearing from 

 a fissure in the edge or on the upper surface of the frond, and consisting 

 of a minute membranous bract or spatha, enclosing 1 or 2 stamens, 

 and a single 1 -celled ovary, with 1 or more ovules, a short style, and 

 no perianth. 



A small, widely distributed genus. 



Roots in clusters. Fronds above 3 lines diameter . . . . 4. L. polyrrhiza. 

 Roots solitary. 

 Fronds very thin, oblong or narrowed at one end (the young 



ones usually projecting on each side at right angles) . . 1. L. trimrfca, 



