MONOCOTYLEDONES' 209 



Properties amd Uses. — Unimportant. 



Order 28. Aeoidace^e, the Arum Order. — Character. — 

 Herbs or shriibs, with commonly au acrid juice, and subter- 

 ranean tubers, corms, or rhizomes. Leaves sheathing, usually 

 net-veined, simple or rarely compound. Flowers unisexual and 

 monoecious, or hermaphrodite, arranged on a spadix within a 

 spathe, or the spathe is absent. Perianth none, or composed of 

 scales which are inferior. Male flower: — Stamens few or 

 numerous ; anthers extrorse, sessile or upon very short filaments. 

 Female flower : — Ovary 1- or more-celled, superior. Fruit 

 succulent. Seeds pulpy, with abundant mealy, horny, or fleshy 

 albumen, or rarely exalbuminous ; embryo various. 



Diagnosis. — Flowers on a spadix, and with or without a true 

 spathe. Flowers naked, unisexual and moncecious ; or herma- 

 phrodite, and then frequently with a scaly inferior perianth. 

 Anthers extrorse. Fruit succulent. 



Division of the Order and Illustrative Genera. — The order 

 may be divided into two sub-orders as follows : — 

 Sub-order 1. Aroidece or Aracece. — Flowers unisexual, monoe- 

 cious. Spadix surrounded by a spathe. Perianth none. 

 Illustrative Genera : — Arum, Linn. ; Caladium, Vent. 

 Sub-order 2. Acorece or Orontiece. — Flowers hermaphrodite. 

 Spadix surrounded by a spathe or naked. Perianth absent, 

 or more generally present, and then scaly. Illustrative 

 Genera : — Acorus, Linn. ; Orontium, Linn. 

 Distribution and Numbers. — They abound in tropical 

 countries, but also occur in cold and temperate regions. There 

 are about 250 species. 



Properties and Uses. — The plants of this order are aU more 

 or less acrid, and often highly poisonous. But this acrid prin- 

 ciple is frequently volatile, or decomposed by heat ; hence it 

 may be in some cases more or less destroyed by drying or ex- 

 posing to heat the parts in which it is found. The best method 

 of getting rid of the acridity is, however, by boihng in water, 

 as the acrid matter is also commonly soluble in that fluid. 

 Starch is usually associated with the acrid principle, and when 

 extracted, may be used for food like other starches. The under- 

 ground stems or corms of many species, when cooked, are eaten 

 in different parts of the world. Some are aromatic stimulants ; 

 others expectorant, antispasmodic, or diaphoretic. 



Order 29. LEMNACB.9s,the Duckweed Order. — Character. — 

 Floating aquatic plants, with lenticular or lobed leaves or 

 fronds. Flowers 2 or 3, enclosed in a spathe (fi^. 974), 



