THE LIFE -HISTORY OF PLANTS. 



U 



removal of the sources of food-supply would entail 

 great loss of time, deficient supply, and deficient 

 quantity ; and a consideration of these facts has led 

 some to advocate the "extension system," wherein 

 pruning- is reduced to a minimum and the plant 

 pretty much left to itself. This practice is un- 

 doubtedly more in accordance with the natural habit 

 of the plant, and may be recommended where there 

 is ample space and no demand for variety or 

 exceptional weight of bunch, but it is inconsistent 

 with the requirements of most gardens as to variety 

 and size of bunch. 



In another class of cases the flowers are produced 

 on the old wood, that is to say, they are formed in 

 summer, remain inactive through the winter, and 

 expand in the following spring, such as Lilacs, 

 Laburnums, Rhododendrons, Crataegus, Weigelas, 

 Elders, some of the Clematis, as those of the patens 

 type, and many others. Such plants are pruned 

 immediately afccr flowering, while the leaves are 

 still on, and opportunity is given for new buds to be 

 formed at once before the advent of winter. 



In the case of most of our fruit-trees the flowers 

 are borne on the shoots of the previous year, as in 

 the Peach, and very generally on short contracted 

 branches called " spm^s," as in the Pear, whose 

 structure, as before pointed out, is different to that 

 of an ordinary branch, and adapted to the storage of 

 a relatively large quantity of food-stuif, to be used 

 up by the buds as they develop. Pruning in these 

 cases is done in winter after the leaves have fallen, 

 and its object is to insure the due proportion between 

 fruit-shoots and extension-shoots, and by the removal 

 of such of the latter as may be needed, to favour and 

 hasten the development of the fruit-buds. Summer 

 pruning and pinching, the bending down or partial 

 fracture of a ieaf-shoot, will often effect the same 

 results. 



E-oot-pruning. — When fruit-trees growing in 

 unsuitable soil are unfruitful, this undesirable state 

 of tbings is sometimes remedied by the process of 

 root-pruning, which essentially consists in the 

 severance of the larger, coarser roots, and th,e pro- 

 duction in consequence of a much larger number of 

 the small feeding-roots, upon which, as we have 

 seen, root-absorption depends. This practice has 

 been adopted from time immemorial, and is still 

 carried out by the Italian peasantr}^ in the case of 

 the Olives. The benefits of root-pruning appear to 

 be dependent on the increased formation of fine 

 feeding-roots near the surface, and to the check to 

 vegetative action on the part of the branches which 

 injury to the roots entails. 



Lifting the roots of fruit-trees every two or three 

 years, or exposing them to the sun for a short time, 



are processes the success of which in inducing fruit- 

 fulness is probably due to the same causes as in the 

 case of root-pruning. All these processes seem to 

 induce a certain amount of precocity or premature 

 development, in consequence of which food- stuff is 

 accumulated at an earlier period than it would 

 otherwise be, and the production of flower-buds 

 thereby favoured, but the exact rationale of the pro- 

 cess is not thoroughly understood. (See on root- 

 pruning of the Apple, pages 320, 321, 322, Vol. II.) 



Propagation. — The injunction " Be fruitful 

 and multiply" applies to plants as to other living 

 creatures, and it is provided for by the processes of 

 nutrition and growth already treated of. For our 

 present purpose it is admissible to distinguish be- 

 tween fruitfulness or reproduction, and multiplica- 

 tion. In plants the formation of buds or of structures 

 equivalent to buds, which may be detached from tho 

 parent plant and give rise to new individuals, 

 enables the gardener to multiply his plants almost 

 at will. The action of the male pollen upon the 

 germ contained in the ovule, as hereafter to be ex- 

 plained, results in the formation of an entirely new 

 individual, a composite of two previously distinct 

 elements. Propagation or multipHcation then may 

 be compared to the separation of one body into a 

 number of parts, each of which is capable of growing 

 on its own account. Reproduction requires the co- 

 operation of two elements. The subsequent phases 

 of growth are pretty much the same in both cases. 



Propagation by buds is seen in a very simple form 

 in some Liver- worts (Sepaticce) and Mosses, wherein 

 small outgrowths take place from the surface of the 

 frond, and, falling into suitable soil, develop into 

 new plants at once. 



On a larger and more complicated scale as to 

 structure may be mentioned the bulbils of the 

 Tiger-lily, the buds of Viviparous Ferns and of 

 Begonias, the tubers of the Potato, and other similar 

 structures familiar to gardeners, and by means of 

 which the plants may be propagated. All these off- 

 sets contain a store of food, and are adapted to take 

 on growth immediately circumstances are propitious. 

 Even where under ordinary circumstances such 

 separable buds are not formed, their development 

 may sometimes be promoted artificially ; thus some 

 plants — e.ff., Gloxinias — may be propagated by peg- 

 ging the leaf down on to the surface of the soil, 

 and by maintaining a suitable temperature. In 

 some cases it is requisite to break the leaf to insure 

 the formation of buds. It is curious to note that the 

 production of tubers on the haulm or stem of the 

 Potato, which is a not uncommon occurrence, is due 

 in like manner, as observed by Mr. A. Dean, to 

 some injury to the stem by twisting or the damage 



