sn 



THjE TROPICAL AGSICULTURIST, 



[Jakvart I, 1884. 



AN ANALYSIS OF TEA. 



It has recently become the custom in selling teas iu New 

 York, to have a sample analysed as a guide to purchasers. 

 The analysis given below was made from a sample of 164 

 packages of Indian tea, of good quality, sold in New York 

 last summer ; and, as it is quite full, we think it will prove 

 of interest to our readers: — 



Per cent. 

 Hygroscopic moisture ... ... ... 5980 



Extract... ... ... ... ... 40350 



Total a,sh ... ... ... ... 5-200 



Ash soluble in water ... ... ... 3'122 



Ash insoluble in water ... .„ ... 2'078 



Ash insoluble in acid ... ... ... "212 



Insoluble leaf ... ... ... ... 53'670 



Tannic acid ... ... ... ..• 10077 



Theiue... ... 2090 



Facing and coloi-ing matter ... "J 



>-Noue. 



Foreign leaves ... 



Exhausted leaves 



— Popular Science Xews. 





SOME OF THE OHAKAOTERISTIOS OF SOILS. 

 In last month's number of Forestrt/^ Mr. D. M'Corquo- 

 dale calls in question a recent remark of one of your 

 contributors to the effect that the annual growth of ' grass, 

 brackens, and other weeds,' in plantations is liable to fur- 

 ther the exhaustion of the soil in such places, and he slyly 

 suggests that if the grasses and weeds bring about ex- 

 haustion, the growth of 100 tons of .saleable timber to the 

 acre must be a serious matter to the soil. But such short 

 and close herbage as 'grass, brackens, and other weeds,' 

 if allowed annually to wither and decay where it has grown, 

 adds considerably to the fertility of the soil; and land under 

 timber stores up each year in the surf.ace soil the food 

 constituents most required by our cropping plants. And 

 this we .shall endeavour to make plain. Out of the sixty- 

 four yet known elements that together go to form our 

 earth, sea, and air, only some twelve or so are found in 

 the auiilyses of plants, and of course these must be present 

 in company with other matter in all soils capable of sus- 

 tamiug vegetation. Of some, however, the plant requires 

 but little, while of others it has to absorb a considerable 

 amount. Those few elements combuiing one with anotherj 

 or one with several, and in various proportions, go to form 

 the many different compoimds which are required to con- 

 stitute a soil fit for cultivation: oxygen and hydrogen unite 

 to form water, hydrogen and nitrogen to form ammonia, 

 calcium and potassium each unite with oxygen to form 

 respectively lime and potash; carbon, nitrogen, and phos- 

 phorus miite with water severally to form carbonic acid, 

 nitric .acid, and pbosiihorie acid; and these three with lime, 

 potash, and soda to form tie carbonates, nitrates, and 

 pho.sphaties of the latter three, and so on. And out of 

 those few the vegetable kingdom elaborates innumerable 

 substances ranging from simple starch to the subtle poisons 

 of the alkaloids. The plant cannot lay hold of and assimil- 

 ate to its substance :my one free and uncombined element, 

 unless perhaps we except the free oxygen of the atmosphere ; 

 when the plant is under certain conditions of growth it 

 cannot avail itself of the free nitrogen of the surrounding 

 ah'. Nor can it absorb any uncombined carbon — the ele- 

 ment th.at forms the great bulk of the plant. Carbon 

 when by itself is a solid and almost insoluble, but combined 

 with oxygen it foi-ms carbonic oxide, a f;as, and plentiful 

 in the atmosphere. Lender certain conditions, owing to 

 some mysterious action of sunlight on the green colouring 

 matter of the tender parts of plants, the plant is able to 

 decompose this oxide by which it is surrounded, and to 

 turn the carbon to its own uses, and also to avail itself 

 of the free oxygen if required. Thus carbon, and oxygen, 

 and watery vapour too, which can penetrate the dehcate 

 outer membranes, are all the substances the plant is able 

 to obtain by means of its leaves and other exposed parts. 

 The rest of its food it must take \\\i by way of its roots. 

 The greater volume of the water it requires is taken up 

 through those channels, and it c:irries with it what it is 

 able to dissolve from the soil. But the active or ab.sorbent 

 parts of the roots have the property of so acting on some 

 matters required by the plants which are insoluble in 

 water that they can pass through the absorbing cells and 



vessels into the sap or general circulating medium of the 

 organism. The potash, lime, soda, and magnesia required 

 are taken up by the roots in the forms of the nitrates, 

 sulphates, phosphates, carbonates, &c., of these bodies, and 

 at the same time the requisite nitrogen, sulphur, phos- 

 phorous, and additional carbon to wliat it can otherwise 

 obtain, passes into the sap. The plant's supplies of nitrogen, 

 phosphorous, and potash, .and perhaps lime as well, though 

 to a less extent, are the most precarious, because these 

 are the scarcest of the essentia! substances of plant food 

 in soils. Enough of the other substances required by the 

 plant are contained in all ordinary soils, and the agricult- 

 urist need not trouble himself over them. Of the four men- 

 tioned, nitrogen is the most valuable, it being the least 

 available ; in fact, the amount of nitrogen available as 

 plant food in any soil is the measure of its fertility. 

 The element is abundant enough, for our .surrounding 

 atmosphere is composed four-fifths of free nitrogen, but 

 then it is one of the most inert of all the elements, and 

 least incUned to combine with others. Under certain natural 

 conditions, combination with others is brought about. The 

 intense heat of lightning flashes causes union between the 

 nitrogen and other elements in the atmosphere. Thus 

 it comes that ammonia and nitric acid can be detected 

 in the air. These are extremely soluble in water, and rain 

 carries them to the soil. From this source alone each 

 acre of soil gets annually something like 75 lb. of nitrogen. 

 All organic matter — remains of animal and plant hfe — 

 contains a large percentage of it, and this finding its 

 way to the soil increases the latter's supply of nitrogen. 

 Coal, peat, deadwood, leaves, dung. &c., contain it in 

 abundance. But it is only when nitrogen is in combin- 

 ation as nitric acid that plants can assimilate it to 

 themselves, and, as we have already said, by way of their 

 roots. Pl.ants cannot make use of the insoluble compounds 

 containiug nitrogen in the soil, but by a wonderful pro- 

 vision of Nature, the nitrogen of those bodies is made 

 available to them. This is accomplished through the means 

 of a minute fungoid organism, whose economy in life 

 seems to be that of attacking the nitrogen of insoluble 

 bodies, and of ammonia as well, and bringing it into 

 combination as nitric acid. Given a due temperature, a 

 fair amount of moistm'C, and sufficient organic or other 

 matter containiug nitrogen, .and the presence of lime or 

 some other base with which to neutralise the acid as it 

 formed, and the process goes on imtirmgly. In early 

 summer it commences with us, and continues far into 

 autumn. The nitrates are so soluble that unless they are 

 speedily taken up by growuig plants they soon find their 

 way to the drains, for ever to be lost to the fields from 

 whence they originated. Phosphorous is rather scanty in 

 soils, and though there is enough in the majority of them 

 for the uses of natural herbage, the growth of cultivated 

 plants necessitates the bestowal of large quiintities of 

 phosphates on land under tillage. Potash is not usually 

 so scarce, for it enters largely into the composition of 

 most of the rooks that form the basis of soils, and as 

 disintegT-ition and decomposition proceeds, fresh stores of 

 it is being placed at the disposal of plants. Experiments 

 on the absorbent powers of soils have revealed the 

 strange fact, that when solutions of potash such as the 

 nitrate, sulphate or carbonate, are pom-ed on soil .and 

 allowed to filter through it, they have the property of 

 arresting, as it were, the potash of any of these salts 

 and substituting lime or soda in its place. Where, how- 

 ever, neither of these alkaline bases or any others are 

 available to act the part of the potash in neutralising 

 the acid, the solutions pass through unaltered, and the 

 potash is found in the filtrate. Soils act similarly with 

 solutions of ammonia, having the power of arresting this 

 most soluble body and preventing its escape to the drains 

 before it h.as taken jiart in the neutrifyiug process before 

 referred to. Hence it follows that lime, besides acting 

 directly as a suppHcr of food to plants, performs many 

 useful oflices in the soil. It acts as a base with which 

 to neutralise the nitric acid produced by the minute fungus 

 already n.entioued. thus saWng the less plentiful potash 

 and ammonia for the uses of the plant; and in like man- 

 ner it neutralises the acids of the soluble phosphates 

 which are nowadays so much used by farmers, and enables 

 the latter to obtain the full good of them. Before the 

 plant has time to seize on the soluble phosphates 



