Fig. 88.

There are some plants that do not emit roots readily from any other point except near their buds, and therefore it is evident that they should be cut at this point, so as to expose that peculiar substance (cambium) from which roots are produced where it is most abundant. Cuttings should always be made with a sharp instrument, for the fibers should be cut off smooth, and not broken or crushed.

The roots produced on a cutting are supposed to be formed from the sap or juices of the plant that have been assimilated by the leaves from the ascending liquid absorbed by the roots. After assimilation has taken place, the sap descends mainly between the bark and wood, but a portion through the bark; and it is from this substance that roots are formed. I am aware that the young branches of some kinds of woody plants having a large pith or hollow stems will produce roots from the inner portion, but this is not sufficient cause to disapprove the general theory of circulation of the sap, or that roots emanate only from the elaborated sap or nascent matter, because it is not impossible nor contrary to the general principles of vegetable physiology that a portion of the true sap of exogenous plants may not pass from the outer to the inner surface of the stems of young one-year-old wood, at least when it is placed under artificial conditions.

There are some authors who contend that a bud, either latent or developed, is essential on a branch to enable it to produce roots - in other words, that roots always proceed directly from a bud; and if a cutting is severed at a distance below a bud, the roots start from the lowermost one, and push their way down under the bark and out at the end, establishing a communication with the source from which they are to derive their future nourishment. It was also once supposed that in the same manner all the buds below the surface of the soil which do not grow upright and form branches, produce roots by going down, overlapping and intermingling with those produced from the upper bud. A similar theory is sometimes advanced in regard to the manner in which a bud or graft unites with the stock upon which it is inserted. Both theories, however, are founded upon error, as can be readily proved by any one who will investigate the subject for the purpose of learning the truth.

The erroneous theory of roots emanating only from buds, doubtless originated from the fact, that many kinds of plants grow more readily from cuttings if they are taken off close to the base of a bud, as before stated, thereby strengthening the belief that at this point only existed the nucleus from which all the roots were formed. To ascertain whether buds must exist on or within a cutting, to enable it to produce roots, it is only necessary to take a section of the stem between the buds (called the internode) of some kind of plant that has no latent buds - for instance, a young shoot of the grapevine, or any similar plant - then make such a cutting produce roots, which it will readily do in the ordinary method. No buds will appear, yet roots will be formed, produced more or less in proportion to the natural vitality of the plant and the amount of available material which it contains. Of course the roots can not grow for any great length of time, nor to any considerable size, without the assistance of buds and leaves to prepare the food which they absorb.

That roots will exist, and continue to grow, feeding upon the food stored up in the plant, and upon that which they absorb, without the assistance of leaves or buds, a much longer period than leaves will without roots, is well known. The tubers of the herbaceous paeonia, for instance, will live and grow for a year or two without a bud or leaf, and its seeds, if sown in the open ground, will generally emit roots and grow the entire season before the leaves even escape from the seed covering.

The only analogy that I could ever discover between a cutting producing roots and a graft or bud uniting with the stock is, that the substance that produces both is the same, unless the grafting of some of the succulent plants which do actually produce roots from the grafts which feed upon the substance of the stock be called proper grafting, which it is not, but is only rooting cuttings in the stems of another plant instead of the soil.

Why one kind of plant will produce roots more readily than another is certainly, at the present time, unknown. Neither is the origin of buds sufficiently understood to allow of any rule being given that would be satisfactory to the practical horticulturist. We know that some plants produce buds from every portion of the stem and roots, which leads us to the conclusion, that every cell is capable, under proper conditions, of producing a plant similar to the original one.

Plants are called compound because they are composed of many buds, each of which may be taken from the parent and compelled to sustain itself as a separately organized structure. The extent to which this subdivision may be carried appears to depend entirely upon the skill of the propagator.

The soil in which cuttings are planted in the open ground should be deep, of a porous nature, and composed of ingredients that will absorb and retain a regular supply of moisture. The variations of climate should be attended with a corresponding variation in soil, which, in warm latitudes, should contain powerful absorbents, so that it will not become too dry in summer; while a soil for the same purpose in the more northern latitudes would be better without these absorbents. In this latitude a loamy soil of fine texture is perhaps the best - one that is not so fine as to break and crack after a shower, or so loose that it will not retain moisture sufficient to supply the wants of the cuttings.

The amount of moisture required by cuttings varies greatly in different species, some requiring little, while others a very large amount. The poplar, willow, and many other kinds of trees will grow more readily if the lower ends of the cuttings are immersed in water containing but very little organized matter. But, as a general rule, cuttings do not require more moisture than is held in suspension in well-drained and friable soil.