SOAP-BOILER'S ASHES 810 



SOIL 



gathered and burnt. Giving them to pigs is another 

 but less sure method of destroying them. Nicotine or 

 soft soap washes will destroy them in the early stages of 

 attack. In the case of the Snowy Fly of hothouses, 

 fumigation and spraying with nicotine wash is efficacious 

 against the fly, but not against the pupae, and the fumi- 

 gation must be repeated. Badly infested leaves should 

 be burned. 



SOAP-BOILER'S ASHES. See ASHES. 

 SOAP-PLANT. Chloro' 'golum pomeridia'num. 

 SOAP TREE. Gymnocla'dus chine'nsis. 

 SOAPWORT. Sapona'ria officina'lis. 



SOBOLE WSKIA. (Commemorative of the Russian, 

 Sobolewsky. Nat. ord. Cruciferse.) 



Hardy, perennial, erect herb. Seeds ; divisions. Well- 

 drained garden soil. 



S. clava'ta (club-shaped). Pure white. Armenia. 1892- 

 litho'phila (stone-loving). White. Tauria ; Caucasus. 



SOBRA'LIA. (Named after F. M. Sobral, a Spanish 

 botanist. Nat. ord. Orchids [Orchidaceas]. Linn. 20- 

 Gynandria, i-Monandria.) 



Stove orchids, grown in pots. See ORCHIDS. 

 S. beyeria'na (Beyerian). i. White, tinted with pink ; 



lip rosy-lilac, yellow. 1892. 

 bla'nda (pleasing). White ; disc of lip golden-yellow. 



1910. 

 Bra'ndtice (Mrs. Brandt's). 4. Rose-purple ; lip 



with yellow throat. S. Amer. 1896. 

 Ca'ttleya (Cattleya-like). Purplish-brown; lip purple, 



with yellow keels. Colombia. 1877. 

 Charleswo' rthii (Charlesworth's). Rich rose-purple ; 



crest bright yellow. Colombia. 1910. 

 chlora'ntha (yellow-flowered). See S. MACROPHYLLA. 

 ditto' 'nice (Clifton's). White, tinted with purple in 



throat of lip. Ecuador. 1910. 



deco'ra (comely). Various. July. Guatemala. 1836. 

 dicho'toma (two-ranked). Rose, purple. March. 



Peru. 



Elizabe'thez (Elizabeth's). See S. LILIASTRUM. 

 fra'grans (fragrant), i. Yellow. Colombia. 1853. 

 Lanthoi'nei (Lanthoin's). Flowers all opening to- 

 gether. Colombia. 1908. 

 leucoxa'ntha (white-yellow). White ; throat of lip 



deep yellow, lined orange-red. Costa Rica. 1888. 

 Lilia' strum (lily- flowered). 3. White. July. Guiana. 



1840. 



ro' sea (rosy). Deep rose ; petals with white veins. 

 Linde'nii (Linden's). 3-4. White, tinted rose ; lip 



crimson-purple. Ecuador. 1895. 

 Lo'wii (Low's), i-ij. Bright purple. Colombia. 



1890. 

 lu'teola (small-yellow). 3. Light yellow, with darker 



veins. Trop. Amer. 1898. 



macro.' ntha (large-flowered). 6. Crimson. Sep- 

 tember. Mexico. 1842. 



a'lba na'na (white-dwarf), i. Pure white. 1897. 

 albida (whitish). Creamy- white ; lip rosy-purple. 



Mexico. 1871. 



Hodgkinso'ni (Hodgkinson's). Lilac ; lip rose- 

 purple and orange. 1894. 

 kienastiafna (Kienastian). White, with a small 



yellow spot on the lip. 1888. 

 na'na. (dwarf). z\. Rose-purple ; lip violet, 



yellow. 1874. 

 pa'llida (pale). Whitish, pale purple, and yellow 



throat. 1873. 



,, purpu'rea (purple). Deep purple. 

 sple'ndens (splendid). 3. Crimson. September. 



Mexico. 1846. 



macrophy'lla (large-leaved). Yellow. June. Panama. 

 ro'sea (rosy). 6. Pale rose. Peru ; Colombia. 

 ,, Ru'ckeri (Rucker's). See S. ROSEA. 

 Sa'nderce (Mrs. Sander's). White. Central Amer. 



1890. 



se'ssilis (stalkless) of Hooker. See S. DECORA. 

 ,, se'ssilis (stalkless) of Lindley. 2-4. Rose-red ; lip 



crimson. British Guiana. (B.M., t. 7376.) 

 suave' olens (sweet-smelling). Pale yellow ; lip white, 



with brown disc. Central Amer. 1878. 

 va'lida (strong), f-i. Whitish- yellow ; lip deep 



orange in front. Panama. 1909. 



S. viola' cea (violet). Violet, white. July. Merida. 

 ,, a'lba (white). White, with yellow throat. 1904. 

 Warsceten'czii (Warscewicz's). Panama. 

 Wiga'nice (Mrs. Wigan's). Soft yellow, shaded with 



rose. 1898. 

 Wilso'ni (Wilson's). White, rose; lip with yellow 



blotch. Central Amer. 

 xantholeu'ca (yellow-white). Sulphur-yellow ; lip 



lemon, with yellow throat. Central Amer. 1882. 

 a'lba (white). Pale primrose. 1889. 



SOCRATE'A. (Commemorative of the great Greek 



Ehilosopher, Socrates. Nat. ord. Palmaceas. Allied to 

 riartea.) 



A stove Palm sending put aerial roots, one to 6 feet 

 from the ground, so that it appears to be standing on its 

 roots. Seeds. Fibrous loam, one-third of lumpy peat, 

 and sand. 



S. exorrhi'za (rooting-out wards). 60-100. Yellow-green. 

 Guiana ; Amazons. 1849. " Zanona Palm." 



SOIL. However varying in the proportions, yet every 

 soil is composed of silica, alumina, lime, magnesia, oxide 

 of iron, salts, and animal and vegetable remains. A 

 fertile soil is one which contains such a proportion of 

 decomposing matter and of moisture as to keep the crop 

 growing upon it always supplied with food in a state fit 

 for the roots to absorb, yet not so superabundantly as 

 to render the plants too luxuriant, if the object in view 

 is the production of seed ; but for the production of 

 those plants whose foliage is the part in request, as spinach 

 or of edible bulbous roots, as onions, which have a small 

 expanse of leaves, so as to be almost entirely dependent 

 upon the soil for nourishment, there can scarcely be an 

 excess of decomposed matter presented to their roots. 



A subsoil of gravel, mixed with clay, is the best, if not 

 abounding in oxide of iron ; for clay alone retains the 

 moisture on the arable surface in too great an excess ; 

 and sand or chalk, on the contrary, carries it away too 

 rapidly. It is, however, evident, that to insure these 

 desiderata in any soil, at all seasons, is impossible ; and 

 it is manifest that a soil that would do so in one climate 

 would fail in another, if the mean annual temperature 

 of them should differ, as well as the amount in inches of 

 rain which falls during the same period. Thus, in the 

 western parts of England, more than twice as much rain 

 occurs as in the most eastern counties, or in the pro- 

 portion of forty- two to nineteen. A soil in the east of 

 England, for any given crop, therefore, may be richer 

 and more tenacious than the soil required for it on the 

 western coast. 



Alumina (clay) imparts tenacity to a soil when applied ; 

 silica (sand) diminishes that power ; whilst chalk and 

 lime have an intermediate effect. They render heavy 

 soils more friable, light soils more retentive. These 

 simple facts are important ; two neighbouring gardens, 

 by an interchange of soils, being often rendered fertile, 

 which before were in the extremes of tenacity and 

 porosity. 



In affording warmth to plants, the earth is of con- 

 siderable importance, and the power of accumulating 

 and retaining heat varies as much in soils as the pro- 

 portions of their constituents. Sir Humphry Davy 

 found that a rich black mould, containing one-fourth 

 of vegetable matter, had its temperature increased, in 

 an hour, from 65 to 88 by exposure to the sunshine, 

 whilst a chalk soil was heated only to 69 under similar 

 circumstances. But the first, when removed into the 

 shade, cooled in half an hour 15 ; whereas the latter 

 lost only 4. This explains why the crops on light- 

 coloured, tenacious soils are in general so much more 

 backward in spring, but are retained longer in verdure, 

 during autumn, than those on black, light soils ; the 

 latter attain a genial warmth the more readily, but part 

 from it with equal speed. 



The quantity of soluble matter obtainable from a soil 

 at any one time is very small, seldom exceeding a one- 

 thousandth part of its weight ; and even pure vegetable 

 mould, the debris of entirely putrefied plants, was found 

 by Saussure to yield only one-eleventh of soluble matter. 

 This mould was top rich for horticultural purposes, peas 

 and beans grown in it being too luxuriant ; and they 

 were more productive in a soil containing only one- 

 twentieth of organic constituents dissolvable by water. 

 Small in amount, however, as are the soluble constituents 

 of the most fertile soils, they are necessary for the 



