Retinispora (Gr. , resin, and , seed), a name proposed by Siebold and Zucca-rini in their Flora Japonica for a genus of coniferoe, which has been accepted until within a few years; but it has since been shown that the resinous coating of the seed, all that distinguishes it from cupressus, is found on undoubted species of that genus; hence it follows that the retinisporas cannot be kept distinct from the cypresses. As it is very difficult to supersede an established name, no doubt these Japanese species, having been introduced as retinisporas, will long retain that name in the catalogues and among arboriculturists. For their botanical characters, see Cypress. The species and varieties, though of comparatively recent introduction, have proved especially suited to the climate of the northern states. In Japan they are 100 ft. or more high, but in our gardens they are thus far only 1 to 6 or 8 ft. high. Like the arborvitae and related plants, the foliage assumes very distinct forms, according to the age of the tree; and some good observers are disposed to regard the 15 or 20 named sorts of our gardens as all forms of a single species.
For small places, these plants are especially valuable; they naturally assume a good form, and may be cut into any desired shape; they are generally upright, but there is one positively pendulous; some have the leaves small, blunt, and scale-like, others sharp and spreading; there are the darkest greens, and varieties with silver and golden variegation, and a collection of these forms presents wide contrasts in habit and color. The plants are for the most part propagated readily from cuttings; these are taken in the autumn, set in sand at a greenhouse temperature all winter, and as the heat increases in spring root rapidly. The leading varieties are here enumerated by the names given in the catalogues, without reference to botanical accuracy. Retinispora obtusa has very dark green, small, blunt, appressed leaves, and there are several varieties. R. pisifera is more slender, and has a golden and silver variety. R. eri-coides is a handsome heath-like plant. R. lycopodioides is much like a club moss. R. filicoides has fernlike branches.
R. plumosa is one of the most valued of all, remarkably compact, with very numerous small branch-lets which give the tree a plume-like appearance; the golden variety of this, R. plumosa, var. aurea, is of great beauty, and is destined to be one of the most popular of all conifers; it has the plumose habit of the green form, but the branchlets and all the spray are of a bright golden hue, and hold this color during the winter months; being easily propagated, it may be used for edgings and for a great variety of ornamental planting.