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-celIed ovary 

 containing 1-8 ovules. 



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



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^ loug, club-shaped. — Rather common 

 in rich damp woods. April-May. 



2. A. Dracontium (L. ) Scliott. Green Dragox. Leaf usually 

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

 acuminate and convolute at the apex, much exceeded by the long (l''-9') 

 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 spathe 

 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. Swket Flac. 2°-5° high. — Very abundant in a 

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



Family 16. LEMNACEAE Dnmort.- 

 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. Lkmna. 



Frond without rootlets. 3. WoLFFlA. 



1. SPIRODELA Schleid. 



Fronds 7-12 nerved. Ovary I)earing two ovules. 



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

 green above, purplisli l)eneath, usually 7-nerved. — Often very common in 

 ponds and ditches. 



