286 RATIONALE OF STRIKING CUTTINGS. emitted roots so abundantly, that I do not think one cutting in a hundred would fail with proper attention. Some of the pots. were placed round the edges of a Melon bed, which affords a very eligible situation where a few plants only are wanted." (Horticultural Transactions, ii. 117.) In this case success appears to have depended upon the following circumstances: 1. The cuttings were prepared in November, at the end of the season of growth, when all the organizable matter required for the cutting was formed, and locked up in the proper places in its interior. It was not necessary, therefore, to take any means of insuring a further supply of aliment. But had it been otherwise, that is to say, if the cuttings had been prepared in the summer, in the midst of their growth, it would have been indispensable to allow a leaf or two to remain attached to the upper end of the cutting, to assist in the formation of alimentary matter. 2. Although but one eye was allowed to grow, yet the cuttings themselves were four or five inches long, and they consisted, to the extent of two-thirds, of two-years-old wood. By this means the quantity of food for the nascent branch was intended to be so great as to insure it against suffering from an inadequate supply, until it had formed roots. The importance of this has already been shown by Mr. Knight in a previous part of this book. 3. The cuttings were taken off in November, and not in the spring. This gave them time to form granulations of cellular substance at the lower or wounded end before the powers of absorption by the alburnum were aroused, and so to protect themselves against a too copious supply of aqueous matter before the growing bud could dispose of it by its leaves. This protection is afforded by the thinnest stratum of new cellular tissue, which covers the ends of the wounded vessels, and acts as a vital filter through which all the crude food must pass from the soil. 4. The lower end of the cuttings was so divided as to be parallel with the bottom of the pot, and it appears from the context, although it is not expressly so stated, that this end was to touch the bottom of the pot. The importance of this pre NEUMANN ON THE SOIL FOR CUTTINGS. 287 caution is well known; cuttings of the Lemon and Orange, which are by no means willing to strike if it is neglected, become young plants readily if it is attended to; and in all difficult cases it is had recourse too. The object of it seems to be to place the absorbent or root end of the cutting in a situation where, while it is completely drained of water, it may, nevertheless, be in the vicinity of a never-failing supply of aqueous vapour. If it were surrounded by earth, water would readily collect about it in a condensed state, and the vessels being all open in consequence of being cut through, would rise at once into the interior; but the application of the root end immediately to the earthen bottom of the pot, with which it is so cut as to be nearly parallel, necessarily prevents any such accumulation and introduction of water, unless over-watering is allowed, and this all good gardeners will take care to avoid. M. Neumann gives the following practical advice as to the earth in which cuttings strike most readily :-" Different sorts of trees do not root equally well in all soils. There are some cuttings which can scarcely be made to succeed in saline earth, while others succeed in it very well. The soils considered the best for striking cuttings in the open air are those which are free, sandy, and soft to the touch. Tamarix elegans and T. germanica prosper in a soil rich in saltpetre; but the Gingko and Poplars cannot strike in it. Cuttings made in glass-houses generally require to be planted in earth mixed with peat in preference to any other, but varied according to the nature of the plant. Whatever composition we use, we must take care not to employ it too dry or too moist; in the first case, the earth not being able to sustain itself in a convenient manner around the cutting, the latter falls or is displaced when we wish to water it; in the second case, the earth being too compact, it hinders the formation of roots; Nature makes vain efforts, and the cutting suffers, decays, and dies, in spite of its disposition to vegetate." Other substances are occasionally employed with some advantage as a substitute for earth, such as chopped damp moss, brick dust, charcoal dust, burnt clay, &c. The three last substances probably act in consequence of their being had conductors of heat, powerful absorbents of gaseous matter, and in the best mechanical state for preserving the cuttings from contact with excess of moisture. An ingenious plan of Mr. Forsyth's is intended to answer this purpose rather more perfectly. He puts a small sixty pot 288 POTS SUITED FOR CUTTINGS. (Fig. XLII. a d) into one of larger size, having first closed up the bottom of the former with clay (a); then having filled the bottom of the outer pot with crocks, he fills up the sides (cc) with propagating soil, in which his cuttings are so placed that their root ends rest against the sides of the inner pot; the latter is then filled with water, which passes very slowly Fig. XLII. through the sides until it reaches the cuttings. (See Gardeners' Magazine, vol. xi., p. 564.) In many cases, especially in striking such plants as Heaths, gardeners employ a stratum of silver sand, placed immediately over the earth in which such plants love to grow. The cuttings are inserted into the sand, but so near the earth that the roots, presently after their emission, find themselves in it, and consequently in contact with a source of food. This sand answers the same purpose as placing the root end of the cutting in contact with the pot, and is an ingenious device for doing that with small cuttings, which cannot be conveniently done otherwise except with large ones. 5. The cuttings are eventually placed in a hot-bed. This is for the purpose of giving them a stimulus at exactly that time when they are most ready to receive it. Had they been forced at first in bottom heat, the stimulus would have been applied to cuttings whose excitability had not been renovated, and the consequence would have been a development of the powers of growth so languid that they probably would not have survived the coming winter: but, the stimulus being withheld till the ADJUSTMENT OF FORCES. 289 cuttings were quite ready for growth, it told with the utmost possible effect. What is demanded when cuttings of plants are to be struck, is a due adjustment of heat, light, and moisture. The first stimulates the vital processes, the second causes the formation of matter out of which roots and leaves are to be organized, the third is at once a vehicle for the food required by the cutting, and a part of it. The great difficulty is to know how to adjust these agents. If the heat is too high, organs are formed faster than they can be solidified; if too low, decay comes on before the reproductive forces can be put in action. When light is too powerful, the fluid contents of the cutting are lost faster than they can be supplied; when too feeble, there is not a sufficiently quick formation of organizable matter to construct the new roots and leaves with. If water is deficient, the cutting is starved; if over-abundant, it rots. It is, then, the adjustment of these forces to the peculiar nature of the cutting to be acted upon that constitutes the art of propagation. It is this which theory cannot supply, but which depends upon skill and experience. If any part of the operations of cultivation can be called empirical, it is this. And yet the operator is not without rules to guide him in this adjustment; the misfortune is, that they are too general. The softer a cutting, the quicker must be the excitement and application of the formative process. The more hard and woody a cutting, the slower will be the operation. The great enemies of the propagator, says Mr. Neumann, are rotting and drying; for this reason cuttings are preserved in the midst of a temperature and humidity always equal, the evaporation of the soil is hindered, and the perspiration of the cuttings is prevented. Heat, light, and moisture being the agents to whose assistance we must look for success, and by whose mismanagement the hopes of the gardener are ruined, it is of the first importance to determine how each can be best and most efficiently controlled. And first of heat. We know that plants are distributed over all parts of the habitable globe; that in neighbouring countries the species are U 290 AMOUNT OF HEAT NECESSARY. nearly alike, that distant countries are clothed with vegetation of entirely different kinds, and that the distinction in the vegetation is in proportion to the distance of the countries from each other. There are not, perhaps, a dozen species in Normandy that do not grow wild on this side the Channel; there are not a dozen species common to England and Bengal. Species, in fact, are in general limited by similarity of tempe rature, and cannot exist beyond such limits. One of the first considerations for the propagator, therefore, is what amount of heat is natural to a species during its season of growth. With less than that it is hopeless to make cuttings grow. It is only when plants strike freely that the natural amount of heat is sufficient; in general they require more. The amount of heat found in their natural climate may be enough for them to grow in; but a greater degree of excitement, by means of a higher temperature, will be demanded by them to strike root in, when cut up into the fragments called cuttings. A Willow-cutting stuck into the open ground will strike root, but it does so faster and more vigorously if placed in a hotbed. A Whitethorn cutting in the open ground will not root at all; in a warm propagating house, it will do so readily; and, to reverse the illustration, cuttings of tropical plants, which naturally enjoy a very high temperature, will perish if it is reduced, and will only put forth roots when it is raised considerably above their natural standard. Thus Mr. Neumann mentions that Nutmegs, Guaiacum, Mangoes, &c., will not succeed unless in a temperature of about 100° Fahr. That degree of heat would be fatal to greenhouse plants. But it is not the temperature of the atmosphere that requires to be maintained above that to which plants are naturally subject it is the soil that must be warmed. The first object is to obtain roots; those organs once formed, leaves will follow. The vital action which causes the production of roots is, in the first instance, local; roots are produced by the development of the cellular matter of the underground part; that cellular matter requires to be stimulated by unusual warmth; but the necessary stimulus cannot be communicated by a heated atmosphere it is the warmth of the soil in which the cellular |