292 PROPAGATION OF PLANTS. 



of the Oak are propagated by grafting. (See Chapter XVII.) But it win 

 be found in practice that the Oaks are rather difficult subjects to deal 

 with, and grafting in the open air should be performed early in spring. 

 Veneer grafting in August, under glass, is the most likely to be success- 

 ful, especially with the evergreen and variegated-leaved Oaks. 



Raphiolepts (Indian Hawthorn). A genus of low-growing ever- 

 green shrubs from China and Japan. They are closely related to the 

 Hawthorns (Vratcegus), with large, thick, dark-green, leathery leaves and 

 white or pink, sweet-scented flowers in pyramidal-shaped clusters. The 

 Japan species (R.Japonicci) is said to be hardy in the gardens of London, 

 England, and will probably succeed here with a slight protection in 

 winter. Propagated by cuttings of the half-ripened shoots planted in a 

 greenhouse or in close frame in the open ground. 



Rettnispora. See Chamcecyparis. 



Rhamnus (Buckthorn). A very large and widely distributed genus 

 of evergreen and deciduous trees and shrubs. There are a half dozen 

 indigenous species, and the common European Buckthorn (It. catharli- 

 cus), formerly used as a hedge-plant in this country, has run wild in 

 many places. The berries of this species were formerly used in medicine, 

 and the juice of the ripe berries yield a pigment called " Sap-green," in 

 common use by water-color painters, while the bark of the branches 

 and roots yield a valuable yellow dye. Propagated by seed, and these, 

 being quite hard, like the Hawthorns, do not usually germinate until 

 the second season, and require the same treatment. 



Rhododendron (Rose-Bay). An extensive genus of evergreen 

 shrubs and small trees, with large, and usually very thick, smooth, green 

 leaves. Taking them as a whole, the Rhododendrons may be placed in 

 the front rank among the most showy and elegant of ornamental plants. 

 There are not only a large number of species, but almost innumerable 

 varieties in cultivation, while new ones appear every year, as hybrid- 

 izing and crossing is readily effected, resulting in wide variation in 

 habit of plant, and in form, size, and color of the flowers. Propagated 

 by seeds, layers, and grafting, and some of the more slender and tender 

 species by cuttings of the young shoots, removed with a heel of the old 

 wood, then plunged in sand in close frames with bottom heat. The 

 seeds are very minute, and must not be covered deeply. They are 

 usually sown in shallow boxes or seed-pans, filled with a mixture of leaf- 

 mold and clean sand, and then placed in a close frame until the plants 

 appear, care being required in watering, lest the seeds are washed out on 

 the surface. When the plants are large enough to handle, remove into 

 other boxes or pans, giving them a little more room for growth, then 

 replace in the frames for a few days, or until the plants become estab- 

 lished in their new position ; after this they may be gradually hardened 

 off by removing the covers of the frames for a few hours at a time. 

 Hardy species and varieties may be planted out in a sheltered position, 

 when a year old, although there will be nothing lost by keeping them. 



