3^^ 



THE TROPICAL AGRICULTURIST. [Dec. i, 1886, 



in just such a manner has beed gathered together a 

 nucleus of iuforuiation arouud which more knowledge 

 cau bd grouped. I may make these points clearer by 

 again quoting an illustration, and, not to confuse or 

 mislead you by going too far afield, I will keep to 

 the same line of investigation, partly because it is 

 quite as simple and conclusive as any other of many 

 that might be selected, and partly because it may 

 be possible to set before you some facts which are 

 interesting or even new to you. 



Hairs. — It has been found that in some cases 

 \»here two plants are growing in the same soil and 

 under the same conditions as above, but where one 

 plant receives less water than the other, that the 

 dwarfed drier plant is more hairy than the larger 

 and luxuriantly growing plant, which has been well 

 watered. On looking more closely into this matter 

 it turns out that the extra hairiness is (in some cases, 

 at any rate) simply due to the fact that the hairs 

 are closer together, because the little cells on the 

 outsr parts of the plant which grow out into hairs 

 do not increase so much in length and superficial 

 extent as those on the well-watered plant, and thus 

 the hairs stand thicker together on the same superficial 

 area of the organ— of a leaf, for instance. In other 

 cases, however, the hairs are really increased in 

 numbers and length— the plant is absolutely more 

 hairy. It will be noticed that details concerning 

 growth and turgidity, and of the influence of various 

 minerals, and so on, are not under consideration here. 

 I am not asserting that all cases of hairiness in plants 

 are to be ascribed to this cause ; but it does occur, 

 as stated, and the point is a curious one in view of 

 the fact that very many plants which grow in sandy 

 dry soils are conspicuously hairy, whereas allied species 

 growing in or near water, or even only in moister 

 situations, are devoid of conspicuous hairs, or even 

 quite smooth. The above peculiarity is not confined 

 to leaves and stems, moreover, for experiments with 

 roots have shown that the root-hairs, which are so 

 important in collecting moisture, &c., from the soil, 

 cau be made to appear in enormous numbers when 

 the root is kept in a soil which is very open and 

 only slightly moist, whereas none or very few are 

 developed on the same roots growing in water: this 

 again is in accordance generally with the fact that 

 the roots of laud-plants growing in light soils develop 

 innumerable root-hairs, whereas those of water-plants 

 do not thus increase their surface and points of 

 attachment. I cannot here go into all the interesting 

 facts known about these hairs, but it will be sufficient 

 if you bear in mind the main points just mentioned. 

 Dkficiency of Watek. — Let us now vary the ex- 

 periments a little. It is obvious that we might suppose 

 any number of differences in the amount of water 

 given to the plants used in the experiments described 

 above: but it would be found, as matter of fact, 

 that however little be the quantity of water given 

 to the soil in which the dwarfed plant is, compared 

 with that put into the soil ia which the luxuriant 

 l>lant grows, the actual weight of water will never- 

 theless have to be considerable, taking the whole life 

 of the plant into consideration — there will be more 

 used than you probably know, moreover, because the 

 soil itself will no doubt condense and absorb some 

 from the atmosphere during the night. There is a 

 minimum of water absolutely necessary, and if the 

 plant does not obtain this it will die. Its death will 

 be ushered in by drooping and withering of the leaves, 

 stem, and roots, and this condition, in which the 

 functions of the plant are interfered with beyond a 

 certain point, passes into a condition of disease. 



Excess of "Watkr. — Now take another case. "We 

 might so arrange the experiment that we poured and 

 continued to pour too much water into the soil. Here 

 again it would be found that a condition of disease 

 eventually sets in — ?.^., a condition in which the 

 functions of the plant are again interfered with 

 beyond a certain point. The symptoms and progress 

 of the disease will be very ditt'erent in the latter 

 case, however, from those in the former. It may 

 also Vie mentioned that in neither experiment is 

 death inevitable if the disturbing cause ia removed 



soon enough — i.e-, if sufficient water be added in the 

 first case before the cells have ceased to be able to 

 take it up, or if the previous conditions of the soil 

 are restored soon enough in the case of the over- 

 watered plant. Here we come to a matter which is 

 less simple than may appear at first sight. You will 

 note that the problem in the latter case is to restore 

 the previous conditions of the roots and soil soon 

 enough; I put it thus, because the conditions of 

 the roots and soil may soon be very profoundly 

 altered by the over-watering. To understand this, it 

 is necessary to become a little more fully acquainted 

 with the condition of affairs in what may be called 

 the normal case, where the soil is light and open, 

 and plenty of water, but not too much, is at the 

 disposal of the roots. Such a soil will consist of 

 innumerable fine particles, of different shapes, sizes, 

 and composition. No doubt there will be grains of 

 quartz, particles of broken up vegetable matter, and 

 little rugged bits of stones containing various minerals ; 

 each of these tiny fragments will be covered with a 

 thin layer of water, and you would probably be 

 greatly surprised if I were to go into the proofs 

 showing how extremely tenacious of its water-blanket 

 each particle is. It may be enough for our present 

 purpose if you accept the fact that it requires enormous 

 force to deprive the particles of the last traces of 

 their water-layers ; they will give off some — or in some 

 cases even a good deal — rather easily, and in fact 

 when the layers become of a certain thickness no more 

 water can attach itself to the particles, but it falls 

 away, and the soil remains saturated, as we say. 



AiE IN THE Soil. — Now these particles of soil, each 

 enveloped in its water-blanket, are not in close contact ; 

 there are spaces between them, and these interspaces 

 influence the quantity of water which can be held 

 back by the soil. Let us suppose such a soil perfectly 

 dry ; the particles above referred to being irregular in 

 shape and size, and only roughly in contact at various 

 points, the interspaces will be filled with air. If 

 water be then added in some quantity, each of the 

 particles becomes clothed with a layer of water, and 

 some of the air is driven out, though bubbles of air 

 will still exist in the larger interspaces. — Gardeners' 

 Chronicle. (Jo he continued.) 



CBOPS ON DRY LANDS IN INDIA. 



TO THE EDITOR OF THE " MADRAS TIMES." 



Sib, — Having received no issue of your journal for 

 the last two months, I happen to be very late, I 

 am sorry, in replying to your remarks, under 

 the head " Dry Lands " in your issue of the 24th 

 ultimo, on a paper on the same subject read by me 

 before the Agricultural Students' Association in March 

 last. With reference to my statement that it will 

 generally be possible to grow on dry land two crops 

 of horsegram for green manure, in addition to the 

 usual crop, you say that the absence or great defi- 

 ciency of moisture in the subsoil and in the air of the 

 interior of the Presidency is the reason why the ryot 

 cannot adopt the plan proposed. Taking this for 

 granted, the absence or deficiency of moisture in the 

 interior of the country is, of course, no reason at all 

 why the ryots in the more favoured Northern Oircara 

 and in the low Carnatic plain should not adopt the 

 plan. Are the dry lands in neighbourhood of the 

 Saidapet Farm, situated under the same or even 

 better circumstances than that estate, cultivated with 

 any more crops during the year than elsewhere ? It 

 cannot be denied "that there are thousands of acres 

 in the Northern Circars and in the low Oarnatic plain, 

 sadly wanting in organic matter, to which, at least, 

 the "plan of green manuring is certainly applicable. 

 As regards the interior parts of the Presidency, one 

 might see there, about the month of June, fair 

 crops of gingelly and cumboo, which are, in fact, far 

 less hardy than horsegram, while the adjacent lands, 

 though similarly circumstanced, are quite bare. The 

 reason why gingelly and cumboo are "not then exten- 

 sively grown is, not that the plants refuse to grow at 

 all, but because the ryots are not certain that the 

 supply of moisture will be enough for their matufa- 



