284 



CCLVI AROIDEvE The Ahum Tribe 



Aroide-k, Juss. Gen. 23. (1789}; R. Brown Rrodr. 333. (1810); Dec. and Duby, 480. (1828); 

 Ldndl. Synops. 246. (1829).— Acorin*:, Link Ilandb. 1. 144. (1829), a § of Junceae. 



Diagnosis. Spacliceous monocotyledons, with simple, succulent, or capsu- 

 lar fruit, a developed spatha, and sub-senile anthers. 



Anomalies. Albumen sometimes absent. In Tacca the ovarium is infe- 

 rior. Spatha absent or rudimentary in some. 



Essential Character. — Flowers diclinous, arranged upon a spadix, frequently naked. 

 Perianthium, either wanting:, or consisting of 4 or 6 pieces. Stamens definite or indefinite, 

 hypogynous, very short ; anthers 1- 2- or many-celled, ovate, turned outwards. Ovarium su- 

 perior, 1-celled, very seldom 3-celled, and many seeded; ovules erect, or pendulous, or parie- 

 tal ; stigma sessile. Fruit succulent or dry, not opening. Seeds solitary or several ; embryo 

 in the axis of fleshy or mealy albumen, straight, taper, with a cleft on one side, in which the 

 plumula lies ; (radicle obtuse, usually next the hilum, occasionally at the opposite extremity. R. 

 Br.) — Herbaceous plants, frequently with a fleshy corjnus, or shrubs ; stemless or arborescent, or 

 climbing by means of aerial roots. Leaves sheathing at the base, either with parallel or 

 branching veins ; sometimes compound ! often cordate." Spadix generally enclosed in a spathe. 



Affinities. The Arum tribe may be considered the centre of a system of 

 organization, of which the other oiders of Spadicere are rays of unequal length. 

 Taking its diagnosis as given above, we shall have it specially known by its 

 highly developed spatha ; Typhacea? will be distinguished by their long anthers 

 and want of spatha, Pandanere by their arborescent habit and drupaceous com- 

 pound fruit, Fluvialcs and Juncagineffi by their want of spatha and return from 

 the spadiceous form of inflorescence, and Pistiacero by their reduction to the 

 simplest state in which flowering plants can exist. The whole of these tribes, 

 taken together, are known by their general tendency to develope their flowers 

 upon a spadix, by their want of floral envelopes, or by those parts not assuming 

 the distinct forms of calyx and corolla, but existing only in the state of herba- 

 ceous scales. With the exception of Pandanece, they are all also known by 

 their plumula lying within a cleft of the embryo ; a structure found in no other 

 monocotyledonous plants, except Grasses, in which the embryo is otherwise 

 widely different. Mr. Brown has remarked that in Dracontium polyphyllum 

 and fcetidum, in which there is no albumen, the plumula consists of imbricated 

 scales, and that it is sometimes double or even triple. In the former of these 

 plants the external scales, in germination, quickly wither away, when other in- 

 ternal and larger ones appear, and remain for some time round the base of the 

 primordial leaf, before the developement of which no rootlets arc emitted. Prodr 

 334. A similar economy has been noticed by Du Petit Thouars, in his genus 

 Ouvirandra. In Tacca it is probable that there are several germinating points 

 upon the embryo, analogous to the double or triple plumula of Dracontium : 

 hence embryos of such a kind may be said to be tubers found in the seed itself. 

 Mr. Brown considers a relation to be established between Aroideac and Aristo- 

 lochice by means of Tacca, in which the ovarium is inferior. Agardh distin- 

 guishes Acoroidea? from Aroidea; by their capsular fruit. 



Geography. Natives of all tropical countries abundantly, but of temperate 

 climates rarely, not extending in Europe further north than 64° north latitude, 

 in the form of Calla palustris, which inhabits the deep, muddy, frozen marshes 

 of southern Lapland. In cold or temperate climates they are usually herba- 

 ceous, while in tropical countries they are often arborescent and of considerable 

 size, frequently clinging to trees by means of their aerial roots, which they pro- 

 trude in abundance. In America, according to Humboldt (Disl. Gtogr. 196), 

 their principal station is on the submontane region between 1200 and 3600 

 feet of elevation, where the climate is temperate and the rains abundant. In 



