54 LEMNACEAE 



FAMILY 15. ARACEAE Neck. 



Herbs with dioecious, monoecious or perfect flowers on a spadix sur- 

 rounded by a spathe. Perianth absent or of 4-6 sepals. Stamens 4-10. 

 Ovary with 1 -several ovules. Fruit berry-like. 



Leaves compound. 1. ARISAEMA. 



Leaves simple and rush-like. 2. ACORUS. 



1. ARISAEMA Mart. 



Perennial from an acrid corm. Flowers dioecious or monoecious at the 

 base of the spadix. Perianth absent. Staminate flowers composed of a 

 few, nearly sessile, 2-4-celled anthers, the pistillate of a 1-celled ovary 

 containing 1-8 ovules. 



Leaf divided into 3 leaflets. 1. A. triphyllum. 



Leaf divided into 7-11 leaflets. 2. A. Dracontium. 



1. A. triphyllum (L.) Torr. JACK-IN- THE-PULPIT. Leaves 1-2, with 

 3 elliptical-ovate leaflets : spathe hooded and curving over the spadix, 

 opened at the throat : spadix 2 / -3 / long, club-shaped. Rather common 

 in rich damp woods. April-May. 



2. A. Dracontium (L.) Schott. GREEN DRAGON. Leaf usually 

 solitary, divided into 7-15 oblong-lanceolate leaflets : spathe oblong, 

 acuminate and convolute at the apex, much exceeded by the long (1 X -9 X ) 

 and slender tip of the spadix. In woods throughout. Well distributed, 

 but nowhere abundant. May. 



2. ACORUS L. 



Herbs from long running, pungent aromatic rootstocks. Scapes 3- 

 angled, similar to the leaves. The spadix seemingly lateral, the spatbe 

 appearing like a continuation of the culm. Flowers perfect, densely 

 covering the spadix. Sepals and stamens 6. Ovary 2-4-celled with several 

 ovules in each cell. 



1. A. Calamus L. SWEET FLAG. 2-5 high. Very abundant in a 

 swamp near the Little Blue River east of Atherton ; Levasy. May. 



FAMILY 16. LEMNACEAE Dumort. 



Minute floating aquatics, consisting of a frond, bearing flowers from 

 the edge or surface. Flowers monoecious, consisting of a single stamen 

 or a single pistil. Ovary bearing 1-6 erect ovules. The species are all 

 known as "Duckweeds." 



Frond with several rootlets. 1. SPIRODELA. 



Frond with one rootlet. 2. LEMNA. 



Frond without rootlets. 3. WOLFFIA. 



1. SPIRODELA Schleid. 



Fronds 7-12-nerved. Ovary bearing two ovules. 



1. S. polyrhiza (L.) Schleid. Fronds 2 // -5 // long, round-obovate, 

 green above, purplish beneath, usually 7-nerved. Often very common in 

 ponds and ditches. 



