232 



THE DICTIONARY OF GARDENING, 



Protoplasm continued. 



The chemical composition of Protoplasm is very com- 

 plex. It belongs to the group of substances similar in 

 nature to white of egg, or albumen. It is very similar 

 in its properties in plants and in animals, in which latter 

 it has been called " sarcode " (from yarns, flesh). When 

 laid in a solution of iodine, it becomes yellowish or pale 

 yellowish-brown. Dyes, such as magenta, eosin, and other 

 aniline colours, carmine, logwood, &o., very generally 

 colour dead Protoplasm readily, especially the nucleus ; 

 but the living substance resists their action. A dilute 

 solution of caustic potash dissolves Protoplasm, and is 

 therefore often used, in microscopical work, to clear it 

 out of sections where the chief desire of the operator is 

 to see the arrangement of the cell walls only. Other 

 tests for distinguishing Protoplasm are also occasion- 

 ally used; but for these, inquirers are referred to such 

 works as Sachs" "Textbook of Botany," Henfrey's 

 " Elementary Course of Botany," Bower and Vine's 

 "Practical Botany," or other works dealing technically 

 with the snbiect. 



PROUSTIA (named after Proust, a Spanish chemist, 

 who died in 1826). OED. Composites. A genus consist- 

 ing of six or seven species of stove or greenhouse, erect 

 or climbing, hoary-tomentose or glabrous, sometimes spiny 

 shrubs, natives of South America and Mexico. Flower- 

 heads small, sessile, homogamous, disposed in much- 

 branched or thyrsoid panicles at the ends or sides of 

 the branches; receptacle naked; corolla bilabiate, with 

 the segments revolute, the outer three- or four-toothed, 

 the inner lip deeply two-parted; achenes tnrbinate or 

 oblong, five-ribbed, with a pappus of copious setae. The 

 under-mentioned species the only one yet in cultivation 

 is a desirable greenhouse climber. For culture, see 

 Mutisia. 



P. pyrifolia (Pyrus-leaved). fl.-heads white; pappus purple. 

 I. petiolate, round-cordate or oval, tomentose beneath ; adult ones 

 coriaceous, densely tomentose beneath, entire or irregularly 

 toothed. Chili, 1865. (B. M. 5489.) 



FRO VENZ ALIA. A synonym of Callc. 



PRUINATE, PRTJINOSE. Covered with glitter- 

 ing particles, as if frosted over. 



PRUMNOPITYS. Included under Podocarpus 

 (which see). 



PRUNELLA (altered from Brunella, derived from 

 the German Die Braune, a disorder in the jaws and throat, 

 which the plants were supposed to cure). The correct 

 spelling, according to Bentham and Hooker, is Brunella. 

 Self-heal. OBD. Labiatce. A small genus (two or three 

 species) of broadly-dispersed, decumbent or sub-erect, 

 hardy perennial herbs. Flowers purplish, bluish, or white ; 

 calyx tubular- campanulate, two-lipped; corolla tube ample, 

 often exserted, the upper Up erect, concave, the lower 

 spreading; whorls six- flowered, in dense, terminal spikes, 

 surrounded by broad, imbricated bracts. Leaves entire, 

 incised-toothed, or pinnatifid. The species are well 

 adapted for ornamenting rockwork, or the front of a 

 flower border. They thrive in any light, rich soil, and 

 may be readily increased by divisions. 

 P. grandiflora (large-flowered), fl., corolla violet or purple, 

 above lin. long, more than twice the length of the calyx 

 August, t petiolate, ovate, often toothed, especially at the base' 

 sometimes sub-hastate, sometimes entire, h. 6in. Europe, 1596. 



SSMTefttS; F?D.ut a ' of which i4 is probably a 



P. hyssoplfolia (Hyssop-leaved). fl. larger than those of 

 P. vulgar^; corolla purplish, rarely white. August. I. sessile, 

 oblong-linear or lanceolate, entire, strigose-nispid. Stems 

 ' nearly ^ 1<>ng> cUiate - hisi d- Mediter- 



P. vulgaris (common). All-heal, fl., calyx purplish; corolla 

 purple, rarely rosy or white, 4m. to fin. long ; whorls in cylindric 

 spikes, lin. to 3m. long. July to September. L lin. to 2in. 

 long, petiolate, the uppermost ones sessile, ovate-oblong or 

 oblong-lanceolate, entire, toothed, or sub-pinnatifid. Stems 

 4in. to 12in long, erect or ascending. Europe (Britain). 

 (by. Lu. B. 1059.) There are several varieties of this species. 



PRUNING. Pruning consists in removing any part 

 of a tree, either stem, branches, or roots, with a view 

 to repressing growth in one direction, and directing the 

 course of sap towards other parts of the tree which are 

 better situated and constituted for performing the natural 

 functions. The work is one of the most important t in 

 gardening, but, when the several habits and modes of 

 fruit-bearing adopted by cultivated trees are understood, 

 it is by no means difficult. Pruning is essential where 

 trees have to be subjected to artificial treatment in a 

 limited space, as in gardens generally, where, for 

 example, a Plum-tree may be grown against a wall, or 

 as a bush, pyramid, or standard. These shapes are 

 produced by a combined system of Pruning and train- 

 ing to prepare trees for filling the several positions 

 assigned them, and contributing a crop from one and 

 all. There are several objects in Pruning, and the 

 results attained vary exceedingly from the time and 

 manner in which the work has been performed, and from 

 other causes, some of which are beyond control. The 

 thinning and removal of superfluous and useless shoots, 

 with a view to admitting light and air, which are essen- 

 tial for insuring productiveness ; the affording of en- 

 couragement towards promoting the formation of blossom- 

 buds on branches hitherto barren ; the modification of 

 form in trained trees; the enlargement of fruit; the 

 removal of dead, dying, or diseased branches, and many 

 other such operations, may be cited as objects for which 

 Pruning may be performed. One of the immediate 

 effects of Pruning is to divert the course of the sap, which 

 has hitherto been utilised by the branch removed, into 

 others which are left; this causes them to strengthen 

 and enlarge, which is one of the results generally aimed 

 at. In the management of fruit-trees, the art of Pruning 

 has a most important bearing, as, under artificial treat- 

 ment, these have often to be cultivated in a limited 

 space, and trained to a shape not in accordance with 

 their natural habits. Again, on the system of* man- 

 agement, in respect of thinning and removing the use- 

 less wood, and exposing that left to become well ripened, 

 depends materially the state of the crops annually 

 secured. The extent to which Pruning may with ad- 

 vantage be practised, depends very much on the subject 

 under treatment, its rate of growth, and many other 

 local circumstances. Some practitioners recommend a 

 free, others a moderate, use of the knife ; and others, 

 again, use it as little as possible consistent with keep- 

 ing their trees within bounds and preserving an evenly- 

 balanced head. On a subject capable of such a wide 

 and varied application, this is scarcely to be wondered 

 at; and as different soils and localities have their own 

 particular influence over the trees grown in them, so 

 does the proper system of treatment vary somewhat in 

 detail. Although hard Pruning is not here recommended, 

 it is considered essential that the system must be mode- 

 rately practised, and the work conducted with a view to 

 preserving an equality and symmetry amongst the branches, 

 which shall also, at the same time, promote vigour and 

 fertility. Young trees are invariably disposed to produce 

 more branches than space can be provided for. By thin- 

 ning out those which are weak and misplaced, addi- 

 tional nourishment is supplied to the others, which may 

 be allowed to develop, and remain almost, or quite, their 

 full length. Where the system of training to be adopted 

 cannot be commenced because of the shoots being im- 

 properly disposed, Pruning must be resorted to, and 

 the sap thereby caused to flow more freely where 

 it is required. If a young fruit-tree can be grown 

 on without much cutting, until it arrives at a bearing 

 state, it has, usually, much cleaner and healthier 

 branches, which, of course, are more favourable to fruit- 

 production than others developed under a system which 

 involves frequent amputation, however much this may 

 be necessary in training to a desired shape. 



