AN ENCYCLOPADIA 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 kopros, 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 and 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 
Brassice) in Turnips; 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- 
Phosphorus—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 
Lime. 8 
PHOTINIA (from photeinos, shining; in reference 
to the leaves). Including Eriobotrya. Ox p. Rosacee. 
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- 
Fic. 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 Bin. 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 euttings or layers. P. japonica is most commonl: 
seen in cultivation. : 
arbutifolia (Arbutus-leaved). Californian Maybush. 
"ES in 9 panicle; petioles and young 
white, 
nches 
