No. 9. 



Di'ainasce of Wet Soils. 



269 



rery liable to lose this indispensable requisite 

 o health. At all events, there can be no 

 ioubt, that all solid food should be perfectly 

 ihevved, and mixed thoroughly with saliva, 

 )efore it passes to the stomach of the animal 

 — the grain crushed, and fibre of hay anJ 

 straw broken by the teeth. To insure tliis 

 ve doubt whether forage should be cut short- 

 ;r than an inch, or an inch and a half. A 

 rentleman who had fed largely with very 

 ine-cut hay, found that much was voided in 

 in undigested state, tinged with blood from 

 .he intestines, and that his cattle, alter a. few 

 iveeks, ceased to thrive. 



Drainage of Wet Soils. 



Tt may be said with safety that the air is 

 he most healthy source of the water for soil, 

 )ut this becomes injurious if, when falling in 

 ;xcess, it is not capable of getting away rea- 

 lily, so as to prevent an undue accumulation : 

 n fact, there is every reason to believe that 

 lurfuce-water, which is for the most part stag- 

 inut, is by far the most injurious, because in 

 his manner the currents produced daring the 

 leat of summer, namely, the period at which 

 'egetation should be most active, will, of ne- 

 ;essity, be entirely from below upwards, 

 leing produced by the evaporation of the wa- 

 er upon the surface of the soil ; and the con- 

 equence will be, that the roots of the plants, 

 nstead of being supplied with water charged 

 vith the valuable gases of the atmosphere, 

 will be glutted with water which has existed 

 o long in the soil that it will have lost these 

 'aluuble ingredients, and will, moreover, be 

 ;harged with excrementitious matters. No 

 ystem of drainage can diminish the quantity 

 if water which a soil receives,- it can only 

 ■ffect the quantity which it retains, and pre- 

 'ent stagnation by allowing it to escape so 

 reely, that continual currents are produced 

 o long as any excess of water remains. 



Water affects the various processes in ve- 

 getable nutrition which occur above ground, 

 •y rendering the atmosphere moist ; and by 

 his means we have reason to believe that 

 hree distinct injuries will be inflicted, two 

 if which are functional and one organic. 

 rhere are two processes of the greatest im- 

 lortance to plants, which take place in the 

 eaves, both of which are effected by the con- 

 lition of the atmosphere as regards moisture 

 —I refer to absorption and evaporation. It 

 s well known that the green parts of plants, 

 >ut more especially the leaves, have the pow- 

 sr during day-light to absorb carbonic acid, 

 ix its carbon and emit the oxygen ; and it is 

 urther known that this process is not only of 

 ntal consequence to plants, but likewise from 

 ts purifying influence on the atmosphere, is 

 )f great importance to the whole animal cre- 



ation ; but this process is greatly interfered 

 with by an excess of moisture, fir the absorp- 

 tion of carbonic acid occurs through small 

 pores in the leaf, wiiich are denominated stc^ 

 mates; these lead into sub-cuticular cells, in 

 the walls of which the process of assimilation 

 goes on. Now, as soon as these cells become 

 filled with water they close, and it conse- 

 quently follows that the absorption of caibonic 

 acid must cease whenever this takes place; 

 of course we need scarcely say, that anything 

 which increases the dampness of the atmos- 

 phere must increase the frequency of this ef- 

 fect, and hence diminish the absorption of 

 carbonic acid. But these stomates have an- 

 other office to perform, for it is through them 

 that evaporation takes place — a process es- 

 sential to the digestion and elimination of the 

 crude sap; the sap, as received by the roots, 

 is in so diluted a statp that it requires to lose 

 two-thirds of its water during digestion before 

 it acquires the proper consistence — all cir- 

 cumstances, therefore, which retard evapora- 

 tion must, in an equal degree, retard diges- 

 tion ; and this evil will, moreover, be still 

 augmented by the necessarily dilute state in 

 which plants will receive their food, from the 

 excess of water existing in the soil. But 

 plants have the power, in a certain degree, 

 of accommodating themselves to circumstan- 

 ces, and in this manner the stomates will di- 

 minish in number, for there are always fewer 

 of them in plants growing in mnrshy places, 

 and thus an organic change will be produced 

 upon the leaf; and it is certain that if plants 

 in a healthy state have naturally a great 

 many stomates, they will no longer thrive, if, 

 tosuit themselves to unnatural circumstances, 

 these pores diminish in number. But it m;iy 

 be asked how it happens that plants should 

 be rendered unhealthy from diminished eva- 

 poration when they possess a greater number 

 of stomates than those natural to marshy 

 places'? to explain which it is merely neces- 

 sary to remember that in marsh plants the 

 cuticle or outer covering of the leaf is so thin 

 that evaporation takes place indiscriminately 

 over its whole surface — and hence stomates 

 are not necessary or required; whereas in 

 plants frequenting dry situations the cuticle 

 is thick, to prevent injury from drought, the 

 stomates being chiefly situated on the under 

 surface of the leaf. It follows, therefore, that 

 plants which naturally inhabit dry situations 

 will be injured by a continual excess of moist- 

 ure in one of two ways — either by diminution 

 of the functions of absorption or evaporation, 

 the structure remaining unaltered ; or, from 

 the leaf acquiring an unnatural organization, 

 by an effort of nature to overcome the prima- 

 ry source of the soil. 



So to the question, how does efficient drain- 

 age remove all the bad effects caused by 



