In the Metanemertini, where the longitudinal stems lie inside the muscular body-wall, definite and metamerically placed nerve branches spring from them and divide dichotomously in the different tissues they innervate.
The Carboniferous forerunners of the tiny club-moss were then great trees with dichotomously branching stems and crowded linear leaves, such as Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria, the largest plants of the period, with trunks sometimes 5 ft.
- Antlers flattened or rounded, without bezor trez-tine, the beam dichotomously forking, and one or both branches again forked, so that the number of tines is at least four; brow-tine forming a right angle or a continuous curve with the beam; coat of adult generally more or less uniform, of young spotted.
- Lateral metacarpals as in Rangifer; antlers rather small, without a brow-tine or sub-basal snag, dichotomously forked, with the upper or posterior prong again forking; tail rudimentary; vomer not dividing posterior nasal aperture of skull.
- Lateral metacarpals as in Cervus; antlers large, without a brow-tine or sub-basal snag, dichotomously forked, with the upper prong of the fork curving forwards and dividing, and the lower prong long, simple, and projected backwards, the beam making a very marked angle with the plane of the face; tail very long; vomer as in Capreolus.
- Lateral metacarpals as in Rangifer; antlers very variable in size, forming a marked angle with the plane of the face, without a brow-tine; when consisting of more than a simple prong, dichotomously forked, frequently with a subbasal snag, and always with the lower prong of the fork projected from the front edge of the beam, in @ome cases the lower, in others the upper, and in others both prongs again dividing; tail long; tarsal gland generally present; metatarsal gland very variable, both as regards presence and position; vomer dividing the inner aperture of the nostrils in the skull into two distinct chambers.
Dichotomously branched as in Macrozamia heteromera.
The upright stems were attached to the soil by a number of dichotomously branched members (Stigmaria), which, whatever their morphological nature may be, appear to have performed the function of roots: they bore numerous cylindrical appendages, which penetrated the soil on all sides.
By the unequal development of the secondary cortex the stem becomes twoor three-lobed; the roots, which branch dichotomously, spring from the furrows between the lobes.
The leaves are highly compound, dividing dichotomously into several leaflets, each of which is deeply pinnatifid, with fine segments.
The dichotomously-branched fronds, of the type represented by several recent species of Gleichenia, e.g.