137 



ALOPECURUS. 



ALUMINITE. 



138 





They require a green-house which is capable of being maintained 

 at a temperature of not less than 40 in the depth of winter, at 

 which time they should have no water whatever ; in the summer they 

 want no fire-heat, but may be watered regularly, the supply being 

 always in proportion to their rate of growth and to the temperature 

 of the air ; that is to say, when in full growth and iu a high tempe- 

 rature, they may have abundance of water, and when growing slowly 

 in a low temperature they should have but very little. 



ALOPECU'RUS, a genus of planta belonging to the natural order 

 Graminaceie. It is distinguished 

 from all other British grasses by 

 its flowers, which grow in close 

 cylindrical heads, consisting of 

 two glumes of equal size and a 

 keeled compressed figure, iu- 

 rWing a single palea, from the 

 base of which arises an arista 

 or beard. It contains many 

 species. 



Alopecurus pratensis, the 

 Meadow Foxtail Grass, is a valu- 

 able plant to the farmer. It is 

 so much larger than any other 

 I'ritijh species of Alopecurus as 

 to be easily recognised ; and from 

 Phltum prataue, which it re- 

 gembles, it may be immediately 

 known by its not having two 

 palese, and by its beard proceed- 

 ing from its palea and not from 

 its glumes. It grows commonly 

 in meadows, where it forms 

 rather a coarse but an abun- 

 dant and early herbage, of 

 which cattle are very fond. 

 In such situations it is in- 

 valuable, but it becomes 

 worthless if sown on light dry Meadow Foxtail Grass (Alopecurta 

 soil. pratensw}. 



A. ayratis, Slender or Field Foxtail Grass, has a fibrous root, and 

 blossoms in July or August. Although a troublesome weed amongst 

 wheat, it is useful for sowing on light sandy soils on the sea-coast. In 

 such situations it grows better than even the common rye-grasses. 

 ALOYSIA, a genus of plants belonging to the natural order 

 iiacea;. A. citrwdora is the Sweet-Scented Vervain of our gardens. 

 [VEBBKNA.] 



ALPINIA, a genus of plants belonging to the natural order Zingi- 

 beraceie. The species have thick tuberous horizontal roots. The stems 

 are numerous and perennial, with lanceolate leaves, having a slit ligulate 

 sheath. The flowers are iu panicles, or loose racemes or spikes. The 

 tube of the corolla is short, the inner limb 1-lipped. The filament of 

 the stamens linear. The fruit is capsular and 3-eelled, with winged seeds. 

 A. tialanga in a native of Sumatra, and is cultivated in the Indian 

 Archipelago. Its roots are pungent, acrid, and aromatic, and are often 

 substituted for ginger. They are sold by druggists under the name 

 of 6V".'-/" <"/"<" A plant related to, if not identical with, the 

 A. esaltata, of Meyer, the Reneulm.i" u-nliiita, of Linnams, is called 

 Curowatti in British Guyana, and is described by Dr. Hancock as 

 a bitter pungent plant, and when taken acting as a diaphoretic and 

 diuretic, and in large doses a emetic. [GALANGA.] 



ALTKKKIi STRATA. In addition to the consolidation and 

 division by cracks, joiuts, and fissures, to which all rocks have 

 been subjected, in unequal degrees, there are special cases of 

 uiic'imjnon induration, internal re-arraugemeut of particles, and even 

 the production of new mineral ingredients, which happen in the strata 

 near to rocks of igneous origin, and along certain great fractures and 

 flexures. Heat is usually appealed to for these effects, and justly; 

 but in addition to mere pervading warmth, Von Buch supposes 

 vaporisation of some ingredients (as magnesia, which converts lime- 

 stone to dolomite), and the solution of others in hot water, to be 

 necessary to explain the various contents of mineral veins. 



ALTERNATION OK GENERATIONS, an expression introduced 

 into natural history by Professor Stcenstrup, a Danish naturalist, to 

 n:ite the difference of form observable between the parents and 

 immediate offspring in the lower animals, as in the Acakplue 

 [Ac .u.Ki'ii.t;], Kaljun [SALPACEJ;], and some others. [GKNEBATIOXS, 

 ALTKHNATF,.] 



ALTH/EA, n genus of plants belonging to the natural order 



<(. It is known by its double calyx, the outer whorl of which 



li ix to nino sepals, whilst the inner has five. A. officinalii is the 



\l 'low, a plant the use of whose mucilaginous roots and leaves, 



in all <-a.<iw in which emollient or demulcent substances are required, 



is of great antiquity. It is a common European plant, and is often 



I in marshes, especially near the sea, in great abundance. It is a 



,;iial, with a carrot-shaped white fleshy root, as thick as the 



thumb, and a foot or more long. The stems are two or three feet 



<1 all over with a soft down, which also is found on the 



, to which it gives a hoary aspect. The leaves are soft, stalked, 



often a little heart-shaped, divided into three or five shallow serrated 

 [obes. The flowers are of a pale rose colour, and appear in very short 

 clusters from the bosom of the leaves ; their calyx is 5-toothed, and 

 surrounded with eight or ten or even more bracts. The corolla and 

 other parts are like those of the Common Mallow. The demulcent 

 lozenges sold in the shops under the Haino of Pate do Guimauve, are 

 made of Marsh-Mallow. 



Marsh-Mallow (Altha-a officinalis 



AltJuea rosea, the Hollyhock, is another species. It is found wild 

 in China, and is now extremely common in our gardens. Linnaeus 

 considered it a distinct genus, which he called Alcea. 



ALUM-ROOT, the root of Geranium maculatmn. It contains alum, 

 and is a powerful astringent. [GERANIUM.] 



ALUM-SLATE, a rock from which, as its name implies, alum is 

 prepared. It is found in Germany, Sweden, &c. ; and in Yorkshire a 

 stratum occurs, which, according to Mr. Winter (Nicholson's 'Journal,' 

 No. 25, p. 241), is 28 miles in length, extending from 10 miles to the 



of the stratum it may be crumbled between the fingers, whereas at a 

 considerable depth it is as hard as roofing-slate. The specific gravity 

 is about 2-48. By exposure to the air it effloresces, and acquires the 

 taste of alum. Alum-slate has not been accurately analysed; it 

 contains silica, alumina, and, before efflorescence, probably pyrites or 

 bisulphuret of iron. 



At Hurlett, near Paisley, and Campsie, near Glasgow, alum is 

 manufactured from what appears to be slate-clay impregnated with 

 bisulphuret of iron ; it is obtained from old coal-pits, and having been 

 long exposed to air and moisture, sulphate of iron and sulphate of 

 alumina are formed, and crystallise so as completely to destroy the 

 texture of the slate. 



This double sulphate of iron and alumina occurs in the form of soft 

 delicate fibres, easily separable from each other ; it is nearly colourless, 

 of a silky lustre, and resembles asbestos in appearance. It is readily 

 soluble in water ; the solution yields crystals of sulphate of iron ; and 

 when potash-salts are added to the remaining solution of sulphate of 

 alumina, crystals of alum are immediately formed ; and this is the 

 process of alum-making already noticed. 



ALUM-STONE, a mineral which occurs in a secondary rock at La 

 Tolfa in Italy, and is there used iu the preparation of alum ; it is found 

 in small masses and veins, and according to Cordier it exists in most 

 burning volcanoes. It is said to be met with also in Tuscany and 

 Hungary. 



This mineral is either massive or crystallised ; the former is usually 

 grayish-white, and sometimes red. It is translucent, easily frangible, 

 scratches calcareous spar, but is scratched by fluor spar. When heated 

 by the blowpipe it decrepitates, and by continuing the heat emits a 

 sulphureous smell. 



The crystals are generally situated in the cavities of the massive 

 substance ; they are small, shining, sometimes externally brownish ; 

 their form is an obtuse rhomboid, variously modified. 



Both varieties have been analysed the massive by Vauquelin, and 

 the crystallised by Cordier ; the results are 



Massive. Crystallised. 



Sulphuric acid . . . 25-00 Sulphuric acid . . . I 

 Alumina . . . . 43-02 Alumina . . . . 3 

 Potash .... 3-08 Fotah .... 10-021 



Silica 24-00 Wattr, a trace of oxide of 



Water .... 4.00 iron and loss . . . 14-830 



100-00 100-000 



ALUMINITE, in Mineralogy, a variety of native Sulphate of 

 Alumina, also called Welisteriie. It is found iu reuiform masses and in 

 botryoidal concretions in Halle in Prussia, Epernay in France, and at 



