478 JiEMNACEJS. (duckweed family.) 



6. ACORUS, L. Sweet Flag. Calamus. 



Spadix cylindrical, lateral, sessile, emerging from the side of a simple 2-edged 

 scape which resembles the leaves, densely covered with perfect flowers. Sepals 

 6, concave. Stamens 6 : filaments linear : anthers kidney-shaped, 1-celled, 

 opening across. Ovary 2-3-celled, with several pendulous orthotropous ovules 

 in each cell : stigma minute. Fruit at length dry, gelatinous inside, 1 - few- 

 seeded. Embryo in the axis of albumen. — Pungent aromatic plants, especially 

 the thick creeping rootstocks (calamus of the shops), which send up 2-edged 

 sword-like leaves, and scapes similar to them, bearing the spadix on one edge ; 

 the upper and more foliaceous prolongation sometimes considered as a kind of 

 open spa the. (The ancient name, from a privative, and nopn, the pupil of the 

 eye, having been used as a remedy for sore eyes.) 



1. A. Calamus, L. Scape leaf-like and prolonged far beyond the (yel- 

 lowish-green) spadix. — Margin of rivulets, swamps, &c. Probably truly in- 

 digenous northward. June. (Eu.) 



Order 108. EEMlVACEiE. (Duckweed Family.) 



Minute stemless plants, floating free on the water, destitute of distinct stem 

 and foliage, being merely a frond, producing one or few monozcious flowers 

 from the edge or upper surface, and commonly hanging roots from under- 

 neath : ovules rising from the base of the cell. Fruit a 1- 1-seeded utricle. 

 Seed large; the apex or radicular extremity of the seed-coat separable as 

 an operculum or lid (as in Cabomba, &c.) Embryo straight, surrounded by 

 fleshy or sometimes very scanty albumen — The simplest, and some of them 

 the smallest of flowering plants, propagating by the proliferous growth of a 

 new individual from a cleft in the edge or base of the parent frond, remain- 

 ing connected for some time or separating, also by autumnal fronds in the 

 form of minute bulblets, which sink to the bottom of the water, but rise 

 and vegetate in spring ; the flowers (in summer) and fruit scarce, in some 

 species hardly ever seen. Frond more or less cavernous ; the upper sur- 

 face furnished with stomata. — These plants may be regarded as a sort of 

 very simplified Araceae. 



Arranged from notes contributed by C. F. Austin, Esq., who is pre- 

 paring a monograph of the American Lemnaceae. 



1. LEMNA, L. Duckweed. Duck's-meat. 



Flowers produced from a cleft in the margin of the frond, usually three to- 

 gether surrounded by a spathe ; two of them staminate, consisting of a stamen 

 only; the other pistillate, of a simple pistil; the whole therefore imitating a 

 single diandrous flower. Sler. Fl. Filament slender : anther 2-celled, didy- 

 mous ; the cells dehiscent transversely : pollen-grains large, spherical, muricate. 

 Fert. Fl. Ovary 1-celled : style and truncate or funnel-shaped stigma simple. 

 Ovules and seeds 1-7. — Fronds producing rootlets underneath, proliferous 



