266 PROPAGATION BY LEAVES. 



p. 297.) There can be no doubt that a great number of plants, both 

 ligneous and herbaceous, may be propagated by joints or half-joints, though 

 cultivators have hitherto made comparatively few trials. 



607. Propagation by bulbs., and entire tubers and tubercles, is effected simply 

 by separating them from the parent plant, and inserting them in the soil about 

 the same depth at which they are found on the parent plant, or a little 

 deeper in very light soil, and not quite so deep if in very heavy soil. A phe- 

 nomenon, Decandolle observes, common to all tubers is this : that while in 

 the seed the radicle or descending part pushes first, in the tuber, on the 

 contrary, the ascending part or plumule is first developed, and the roots 

 appear a short time afterwards. The potato and the Jerusalem artichoke 

 are often planted by entire tubers, as well as by separating them into eyes 

 or sets. The same may be said of the tubers of the anemone and the 

 ranunculus. The tubercles or small tubers of saxifraga granulata, adoxa 

 moschatellina, and of many species of oxalis, are propagated by planting the 

 tubers entire. The offsets of all bulbs are also planted entire, and, as 

 already observed, they may be considered as buds ; though they differ from 

 ordinary buds, in which the nutritive matter is laid up in the alburnum of the 

 plant, by having it deposited at the base of the leaves or scales of which the 

 bulb is composed. 



608. Propagating by bulb-bearing leaves. The leaves of malaxis paludosa 

 bear little bulbs at their extremities; several sorts of allium originate bulbs in 

 the axils of the bracts ; and in some ferns, such as asplenium bulbiferum, 

 and Woodwardia radicans, bulbs are found at the extremities of the leaves, 

 which when these touch the soil, grow, throw down roots, and produce 

 young plants. Bulbs, or germs analogous to them, are found in marchantia 

 polymorpha, and on many arums and dioscoreas, by all of which the plants 

 may be propagated ; taking care, in difficult cases, to preserve the soil, on 

 which the bulbs are placed, uniformly moist, shaded, and at a somewhat 

 higher temperature, and the atmosphere, by means of a bell-glass, in a 

 greater degree of moisture, than is required for the parent plant. 



3. Propagation by Leaves. 



This mode of propagation is of considerable antiquity, though it has not 

 till lately been much practised. It is said by Agricola, (Z/ Agriculteur Par- 

 fait, <5fc., ed. 1732) to be the invention of Frederick, a celebrated gardener at 

 Augsburg, and to have been first described by Mirandola, in his Manuale di 

 Giardinieri, published in 1652. Subsequent experiments by C. Bonnet, of 

 Geneva ; Noisette, Thouin, Neuman, and Pepin, of Paris ; Knight, Herbert, 

 and others, in England ; and quite recently by Lucas, in Germany, have proved 

 that there is no class of plants which might not be propagated by leaves. It has 

 been tried with success with cryptogamous plants, with endogens and exogens; 

 with the popular divisions of ligneous and herbaceous plants, annuals, bien- 

 nials, and perennials, and with the leaves of bulbous plants and palms. 



609. The principle on which the propagation of plants by leaves is founded 

 is considered by some as the organisability of the sap of the plant, and by 

 others as founded on the universal diffusion through the plant of embryo buds. 

 " That the vital power residing in the latex or blood of the plant," Mr. 

 Lymburn observes, " is sufficient to form buds, no one can doubt who has 

 observed the matter extravasated at times from the stems of geraniums, 

 dahlias, &c., and the stumps of old trees. At first it is only a mass of 

 cellular matter, but gradually begins to thicken on the surface, and get of 



