This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
This genus is so near the last that it might well be included in it, but this is not the place to introduce any changes in the nomenclature of plants, and possibly this may be as good a genus as many others. The principal distinction resides in the seeds, which are covered with resinous vesicles, giving rise to the generic name, from resin, and seed.
These shrubs are included under the genus Chamcecyparis by some writers. Some of the forms described as species are probably not entitled to that rank. They are all from Japan.
1. R. pisifera. - A small tree with very slender feathery branchlets and scale-like very acute imbricate slightly spreading leaves of a yellowish-green tinge, glaucous beneath. Fruit very small, about as large as a medium pea. This is a very distinct shrub of somewhat irregular habit, and it appears to be quite hardy in the South of England. There is a variety aiirea with gold and green variegated foliage, and a variety argentea with silvery foliage.
2. R. obtusa.- A very beautiful species, forming a tree of 60 to 100 feet in Japan. Young plants of it are densely branched shrubs with closely imbricated decurrent obtuse tubercled leaves of a deep vivid green, silvery below or in shady places. Fruit larger than in the last. A very desirable hardy shrub. R. lyco-podioldes is said to be a variety of this in which some of the leaves are subulate and spreading. There are also the varieties aurea and argentea with gold and silver variegated foliage; and a miniature form called pygmcea, syn. Thuja pygmaea.
R. ericoides, syn. Cupressus ericoides, a well-known compact conical dwarf bush, and the first of the genus cultivated in this country, is considered by some as the primordial form of R. obtusa, and by others it is referred to R. leptoclada. In this all the leaves are linear and spreading, densely arranged in four ranks on the slender branchlets, somewhat rigid and acute, bright green above and glaucous beneath, assuming a ruddy tint in winter. It grows from 2 to 4 feet high.
3. R. plumosa. - The varieties ranged under this name are exceedingly beautiful dwarf shrubs with very dense slender flexible feathery branchlets dotted with acicular more or less spreading leaves. The one called argenteo-variegata resembles ericoldes in its foliage, except that it is soft, silvery and pale green; but the branches are less regular, and the branchlets slenderer and flexible. Probably this and the other varieties under this name belong to some of the other species.
4. R. squarrosa. - A dwarf spherical shrub with slender drooping branches and minute imbricate scale-like foliage of a silvery green. It is reported as being rather tender.
R. leptoclada, syn. R. squarrosa leptoclada, is a more erectgrowing compact shrub with glaucous green imbricate foliage. It is said to be quite hardy in England.