276 



CULINAEY OR KITCHEN GARDEN. 



quite as necessary to furnish heat for the soil 

 as for the air ; not, however, heat without mois- 

 ture, for that would evidently produce much 

 greater evils than it was intended to cure, as 

 has indeed been found by inconsiderate expe- 

 rimenters. I quite agree," continues the doctor, 

 " with Mr Writgen in believing that it is the 

 temperature and moisture of a soil, much more 

 than its mineralogical quality, that determine 

 its influence upon vegetation." 



Moisture in the soil. — " Water," continues the 

 same authority, " is one of the most important 

 elements in the food of plants, partly from their 

 having the power of decomposing it, and partly 

 because it is the vehicle through which the so- 

 luble matters found in the earth are conveyed 

 into the general system of vegetation. Its im- 

 portance depends, however, essentially upon its 

 quantity. We know, on the one hand, that 

 plants wiU not live ia soU which, without being 

 chemically dry, contains so little moisture as to 

 appear dry ; and, on the other hand, an exces- 

 sive quantity of moisture is, in many cases, 

 equally prejudicial. The great point to deter- 

 mine is, the amount which is most congenial 

 to the constitution of the plant. The effect of 

 continuing to make plants grow in a soil more 

 wet than suits them, is well known to be not 

 only a production of leaves and ill-formed 

 shoots, instead of flowers and fruit, but, if the 

 water is in great excess, of a general yellow- 

 ness of appearance, owing, as some chemists 

 think, to the destruction by the water of a blue 

 matter, which, by its mixture with yellow, 

 forms the verdure of vegetation. If this condi- 

 tion is prolonged, the vegetable tissue enters 

 into a state of decomposition, and death ensues. 

 In some cases the joints of the stem separate, 

 in others the plant rots off at the ground ; and 

 all such results are increased in proportion to 

 the weakness of light and the lowness of tem- 

 perature. DecandoUe considers that the col- 

 lection of stagnant water about the neck of 

 plants prevents the free access of the oxygen 

 of the air to the roots ; but it seems to me," 

 says Dr Liudley, " that much more mischief is 

 produced by the coldness of the soil in which 

 water is allowed to accumulate. It seems also 

 probable that the extrication of carburetted hy- 

 drogen gas is one cause of the injury sustained 

 by plants whose roots are surrounded by stag- 

 nant water; but upon this point we want 

 much more satisfactory evidence than we yet 



Stones are valuable in all soils, as they, in 

 general, are composed of the same material as 

 the soil itself, and, indeed, may be considered as 

 the soil in a previous state. By their gradually 

 crumbling down by the action of air, frost, and 

 moisture, they are continually adding new im- 

 palpable matter to the soU. As a considerable 

 portion of this impalpable matter is annually 

 consumed by planlf^, were it not for the pre- 

 sence of stones the soil would ultimately become 

 sterility itself. The practice, therefore, of raking 

 ofl' stones is just removing so much of the soil 

 itself; and the iU effects of this have been long 

 ago observed by cultivators, while they were 

 ignorant of the cause — so much so, it has been 



stated that some farmers, finding their land so 

 much deteriorated after the removal of the 

 stones, returned them again, after which the soil 

 regained its former fertility. 



Impalpable matter in the soil — that is, matter 

 not .to be perceived by.touch — is of vast import- 

 ance to vegetation, and is a product of both 

 organic and inorganic matters. Its functions are 

 exceedingly complicated, and are thus spoken of 

 by Dr Madden : " In this portion of the soil, 

 the mineral and organic matter are so com- 

 pletely united, that it is quite impossible to 

 separate them from each other ; indeed, there 

 are weighty reasons for believing that they are 

 chemically combined. It is from this portion 

 of the soil that plants obtain all their mineral 

 ingredients, and likewise all their organic por- 

 tions, in so far as these are obtained by the 

 roots ; in fact, plants receive nothing from the 

 soil except water, which has been associated with 

 that portion which is at present engaging our 

 attention. 



The particles forming the impalpable matter 

 are in such close apposition that the whole acts 

 in the same way as a sponge, and is hence capar 

 ble of absorbing liquids and retaining them. It 

 is in this way that soil remains moist so near the 

 surface, even after a long-continued drought ; 

 and I need not say how valuable this property 

 must be to the plants, since by this means they 

 are supplied with moisture from below, brought 

 up by the capillary action of the soil during the 

 heat of summer, when otherwise, unless artifi- 

 cially watered, they would very soon perish. 



Another most useful function of this impal- 

 pable matter, is its power of separating organic 

 matter from water in which it has been dissolved. 

 Thus for example, if the dark-brown liquid 

 which flows from a dunghill is taken and poured 

 on the surface of some earth in a flower-pot, and 

 a sufficient quantity added to soak the whole 

 earth, so that a portion flows out at the bottom 

 of the pot, this latter liquid will be fo<md much 

 lighter in colour than before it was poured upon 

 the earth ; and this effect will be increased, the 

 nearer the soil approaches in its nature to the 

 subsoil. Now, as the colour was entirely owing 

 to the organic matter dissolved in it, it follows 

 that the loss of colour is dependent upon an 

 equivalent loss of organic matter ; or, in other 

 words, a portion of the organic matter has en- 

 tered into chemical combination with the impal- 

 pable mineral matter, and has thus become 

 soluble in water. The advantage of this is, that 

 when soluble organic matter is applied to soil, 

 it does not all soak through with the water, and 

 escape beyond the reach of the roots of the 

 plants, but is retained by the impalpable por- 

 tions in a condition not liable to injury from 

 rain, but still capable of becoming food for plants 

 when it is required." Hence liquid manure may 

 be applied to the soil at any period of the year — 

 an opinion that has been disputed by those who 

 have not fully considered the matter. 



The surface of soils is of vast importance, be- 

 cause on its inclination greatly depends the pro- 

 per amount of moisture retained by the soil for 

 the growth of plants. If too steep, it throws off 

 the rain too rapidly ; and if too flat, it often retains 



