Order 5. =Araceæ= (=Arums=). The flowers are small, and always borne _without bracts or bracteoles_ on _an unbranched_, often very fleshy spike, which is enclosed by a spathe, often petaloid and coloured (Fig. 301). The fruit is a _berry_. Outer integument of the seed fleshy.--The leaves have generally sheath, stalk, and blade with distinctly _reticulate_ venation; they are chiefly cordate or sagittate (Fig. 302), seldom long with parallel venation as in the other Monocotyledons (_Acorus_, Fig. 300). The Araceæ are quite _glabrous_, generally _perennial herbs_ with tubers or rhizomes. Many have latex.--For the rest the structure of these plants varies; for example, while some have a perianth, in others it is wanting; in some the perianth-leaves are free, in others united; some have hermaphrodite flowers, but the majority unisexual (monœcious); some have free, others united stamens; the ovules are orthotropous, anatropous, or campylotropous, erect or pendulous; the ovary is 1–many-locular; some have seeds with endosperm, others without. ~_In habit_ there are great differences. While some, _e.g. Colocasia_ (Fig. 302), have a thick, more or less upright stem, with leaf-scars, but not woody, others are climbers, epiphytic, and maintain themselves firmly by means of adventitious roots, on the stems and branches of trees, or even on steep rocks, _e.g. Philodendron_; the cordate, penninerved leaf is the most common (Fig. 302), but various branched forms appear; the pedate leaves of _Helicophyllum_, _Dracunculus_, etc., are cymosely branched; the leaves of _Monstera deliciosa_, perforated by tearing, should be noticed (the vascular bundles while in the bud grow faster than the tissue between them, causing the latter to be torn, and the leaf perforated). With regard to the anatomical structure, the presence or absence of latex, raphides, resin-passages, groups of mucilage-cells should be noted. Engler makes use of these anatomical peculiarities for a scientific arrangement of the order.~ =A.= ORONTIEÆ, CALAMUS-GROUP. ☿, hypogynous flowers of a completely formed monocotyledonous type (number in the whorls 2, 3, or 4).--_Acorus_ (_A. calamus_, Sweet-flag) has a regular, 3-merous, pentacyclic flower (Fig. 300 _C_, _D_). They are marsh-plants, with creeping rhizome, triangular stem, and long, sword-like leaves (Fig. 300 _A_); the inflorescence is terminal, apparently lateral, being pushed to one side by the upright, sword-like spathe (Fig. 300 _B_).--~_Anthurium_ (Pr2+2, A2+2, G2); _Pothos_; _Orontium_ (unilocular ovary with one ovule), etc.~ [Illustration: FIG. 300.--_Acorus calamus_: _A_ habit (much reduced); _B_ inflorescence; _C_ a flower; _D_ diagram; _E_ longitudinal section of an ovary; _F_ an ovule.] [Illustration: FIG. 301.--_Arum maculatum._ The spathe (_h_) in _B_ is longitudinally divided.] [Illustration: FIG. 302.--_Colocasia Boryi._]