AN ENCYCLOPEDIA OF HORTICULTURE. 



107 



Phosphates of Lime continued. 



is referred to works on chemistry, such as Miller's 

 " Elements of Chemistry," or Johnston and Cameron's 

 " Elements of Agricultural Chemistry and Geology." Soils 

 generally contain a small quantity of the Phosphates of 

 Lime, but not enough for the requirements of cultivated 

 plants, as each crop removes some of the small supply, 

 which, in time, becomes exhausted. Hence, it is neces- 

 sary to add to the soil new supplies of Phosphates ; and 

 this is largely done by means of artificial manures. 

 The chief sources of Phosphates are bones and copro- 

 lites, which latter are hard, grey or brown, rounded 

 pebbles, abundant in certain localities in England. They 

 were formerly believed to be the fossilised dung of 

 animals (from the Greek word Tcoproa, dung). They are 

 probably the fragments of bones of great reptiles that 

 lived in the period to which the rocks and strata (Green- 

 sand) in which they are found belong. There are also 

 other less important sources of the mineral. The Phos- 

 phate contained in bones and in coprolites is not 

 soluble in pure water, but is so in acetic acid and in 

 the stronger acids. Experiments show that various sub- 

 stances insoluble in water are rendered soluble by con- 

 tact with the roots of plants, probably by means of the 

 excretion of an acid from them. Bone Phosphate is 

 acted on in this way, and the effect is largely in- 

 creased when the bones or minerals are in a finely- 

 powdered state. Bone-dust, prepared by grinding 

 bones, after they have been steamed, to remove the 

 animal matter, and thus render them more easy to 

 reduce to powder, and ground coprolites and mineral 

 Phosphates, are now largely used as manures. In 

 this form, the Phosphates have the advantage of 

 remaining in the soil for a considerable time, until 

 absorbed by the roots of plants ; hence, their 

 action is spread over more than one year. 

 It is, however, frequently desired to allow 

 plants to absorb them more rapidly than 

 can be done where the roots have to render 

 the Phosphates soluble. To permit of this, 

 the Soluble Phosphate, or Superphosphate 

 of Lime is made use of. It is prepared by 

 subjecting bones, or a mixture of bone-ash 

 and mineral Phosphates, to the action of 

 sulphuric acid (oil of vitriol), in the pro- 

 portion of about three parts of the Phos- 

 phates to two of acid. The commercial 

 Superphosphate is a somewhat indefinite 

 substance, composed of the soluble Phos- 

 phate of Lime in large proportion, along 

 with small quantities of the insoluble Phos- 

 phates arid a good deal of sulphate of lime. 

 The soluble Phosphate readily dissolves in 

 water, and plants obtain it in larger pro- 

 portion the first season after it is put on 

 the soil; but it is liable to be washed out 

 of the soil by rain : hence, its effects are 

 not lasting. It should be mixed with two 

 or three times its bulk of ashes or mould 

 before sprinkling it on the soil. It is 

 asserted by Mr. Jamieson, as the result of 

 his experiments, that Superphosphate of 

 Lime favours the development of " Finger- 

 and-Toe " (the work of Plasmodiophora 

 Brassica>) in Turnips j but this is denied by others, who 

 advocate its use. 



PHOSPHORUS (from the Greek words phos, light, 

 and phoreo, I bear ; in allusion to its being luminous in 

 the dark). One of the chemical elements found in all 

 living beings. It always occurs, in nature, combined 

 with several other elements, and cannot remain in its 

 usual form exposed to the air without undergoing 

 change, since it unites with one of the gases (oxygen) 

 that make up the air. A well-known, nearly inert modi- 



Phosphoms continued. 



fication of Phosphorus in the air is that made use of to 

 tip the ends of lucifer matches. 



There is still much uncertainty regarding the use or 

 uses of Phosphorus in plants, but it is believed that it 

 aids in building up the protoplasm, or actual living 

 substance, of the bodies of both plants and animals, as 

 well as in the transference of the protoplasmic sub- 

 stances from the cells in which they are formed to 

 the parts in which they are to be employed, in supply- 

 ing food to old tissues, or in forming new cells. The 

 combinations in which plants obtain the supply of 

 Phosphorus necessary for them are almost wholly the 

 phosphates of lime ; of which several exist, differing 

 among themselves in the percentage they contain of 

 the aliment calcium (which is the base in lime), and 

 in their solubility in water. See Phosphates of 



PHOTINIA (from photeinos, shining ; in reference 

 to the leaves). Including Eriobotrya. OBD. Rosacece. 

 A genus comprising about a score species of half- 

 hardy, evergreen shrubs or trees, natives of the moun- 

 tains of India, China, and California. Flowers frequently 

 white, disposed in terminal corymbs or panicles ; calyx 

 with a campanulate or turbinate tube and five ovate, 

 obtuse lobes ; petals five, spreading ; stamens about 

 twenty. Drupe or berry ovoid, in some species edible, 

 one to five-celled, the cells one or two-seeded. Leaves 

 alternate, short or long-stalked, coriaceous, simple, en- 

 tire or serrate ; stipules sometimes almost leaf-like. 

 Photinias are very handsome-leaved shrubs for sheltered 

 situations, and for culture against walls. In cold parts 

 of the country, and during severe weather, some pro- 



FIG. 125. FRUITING BRANCHLET OF PHOTINIA JAPONICA (much reduced). 



tection is essential. They prefer a rather light, loamy 

 soil, and do not succeed well if it is very stiff. Propa- 

 gated by cuttings of side shoots, 2in. or Sin. long, 

 inserted in sandy soil, under a bell glass ; also, in the 

 open air, in April, by cleft-grafting, close to the ground, 

 on stocks of common Quince. These may be procured 

 from cuttings or layers. P. japonica is most commonly 

 seen in cultivation. 



P. arbutlfplla (Arbutus-leaved). Californian Maybush. fl. white, 

 disposed in an elongated panicle ; petioles and young tranche* 



