1838] 



FARMERS' REGISTER. 



629 



certain plants from the atmosphere. It prevents 

 the action ot' oxygen I'rom being too energetic, 

 and serves as a nieiiinm in whicli the more essen- 

 tial parts of ihe air act: nor is this circumstance 

 unconformable to the analogy o( nature ; for the 

 elements most abundant on the solid surllice of 

 the globe, are not those which are '.he most essen- 

 tial 10 the existence of the living beings belong- 

 ing to it. 



The action of the atmosphere on plants differs 

 at different periods of their growth, and varies 

 with the various stages of the developement and 

 decay of their organs. Some general idea of its 

 influence may have been gained from circum- 

 stances already mentioned : I shall now refer to it 

 more particularly, and endeavor to connect it with 

 a general view ot the progress of vegetation. 



If a healthy seed be moistened and exposed to 

 air at a temperature not below 45*^, it soon ger- 

 minates ; it shoots forth a plume which rises up- 

 wards, and a radicle which descends. 



If the air be confined, it is found that in the 

 process of germination the oxygen, or a part of it, 

 is absorbed. The azote remains unaltered ; no 

 carbonic acid is taken away from the air ; on the 

 contrary, some is added. 



Seeds are incapable of germinating, except 

 when oxygen is present. In the exhausted re- 

 ceiver of the air-pump, in pure azote, in pure car- 

 bonic acid, when moistened they swell, but do 

 not vegetate ; and if kept in these gases, lose 

 their living powers, and undergo putrefaction. 



If a seed be examined before germination, it 

 will be found more or less insipid, at least not 

 sweet ; but after germination it is always sweet. 

 Its coagulated mucilage, or starch, is converted 

 into sugar in the process ; a substance difficult of 

 solution is changed into one easily soluble ; and 

 the sugar carried through the cells or vessels of 

 the cotyledons, is the nourishment of the infant 

 plant. It is easy to understand the nature of the 

 change, by referring to the facts mentioned in the 

 third lecture ; and the production of carbonic acid 

 renders probable the idea, that the principal che- 

 mical difference between sugar and mucilage de- 

 pends upon the sugar containing a larger propor- 

 tion of the elements of water, and upon a slight 

 difference in the proportions of their carbon. 



The absorption of oxygen by the seed in ger- 

 mination, has been compared to its absorption in 

 producing the evolution of frntal life in the egg ; 

 but this analogy is only remote. All animals, 

 from the most to the least perfect classes, require 

 a supply of oxygen.* From the moment the 



* The impregnated eggs of insects, and even of 

 fishes, do not produce young ones, unless they are sup- 

 plied with air, that is, unless the foetus can respire. 

 I have found that the eggs of moths did not produce 

 larvae when confined in pure carbonic acid ; and 

 when they were exposed in common air, the oxygen 

 partly disappeared, and carbonic acid was formed. 

 The fish in the egg or spawn gains its oxygen from the 

 air dissolved in water; and those fishes that spawn in 

 spring and summer in stdl water, such as the pike, 

 carp, perch, and bream, deposit their eggs upon suba- 

 quatic vegetables, the leaves of which, in performing 

 their healthy functions, supply oxygen to the water. 

 The fish that spawn in winter, such as the salmon and 

 trout, seek spots where there is a constant supply of 

 fresh water, as near the sources of streams as possible, 

 and in the most rapid currents, where all stagnation is 

 prevented, and where the water is saturated with air. 



heart begins to pulsate till it ceases to beat, the 

 aeration of the blood is constant, and the function 

 of respiration invariable ; carbonic acid is given 

 off' in the process, but the chemical change pro- 

 duced in the blood is unknown ; nor is there any 

 reason to suppose the formation of any sub- 

 stance similar to sugar. In the production of a 

 plant from a seed, some reservoir of nourishment 

 is needed before the root can supply sap ; and this 

 reservoir is the cotyledon, in which it is stored up 

 in an insoluble form, and protected, if necessary, 

 during the winter, and rendered soluble by agents 

 which are constantly present on the surface. The 

 change of starch into sugar, connected with the 

 absorption of oxygen, may be rather compared to 

 a process of lermentationthan to that of respira- 

 tion ; it is a change effected upon unorganized 

 matter, and can be artificially imitated ; and in 

 most ot" the chemical changes that occur when 

 vegetable compounds are exposed to air, oxygen 

 is absorbed, and carbonic acid formed or evolved. 



It is evident, that in all cases of tillage the seeds 

 should be sown so as to be fully exposed to the in- 

 fluence of the air. And one cause of the unpro- 

 ductiveness of cold clayey adhesive soils is. that 

 the seed is coated with matter impermeable to 

 air. 



In sandy soils the earth is always sufficiently 

 penetrable by the atmosphere; but in clayey soils 

 there can scarcely be too great a mechanical divi- 

 sion of parts in the process of tillage. Any seed 

 not fully supplied with air, always produces a 

 weak and diseased plant. 



The process of malting, which has been alrea- 

 dy referred to, is merely a process in which ger- 

 mination is artificially produced; and in which the 

 starch of the cotyledon is changed into sugar; 

 which sugar is afterwards, by fiirmentation, con- 

 verted into spirit. 



It is very evident from the chemical principles of 

 germination, that the process of malting should be 

 carried on no further than to produce the sprouting 

 of the radicle, and should be checked as soon as 

 this has made its distinct appearance. If it is 

 pushed to such a degree as to occasion the perfect 

 developement of the radicle and the plume, a con- 

 siderable quantity of saccharine matter will have 

 been consumed in producing their expansion, and 

 there will be less spirit formed in fermentation, or 

 produced in distillation. 



As this circumstance is of some importance, I 

 made in October, 1806, an experiment relating to 

 it. I ascertained by the action of alcohol, the re- 

 lative proportions of saccharine matter in two 

 equal quantities of the same barley; in one of 

 which the germination had proceeded so tiir as to 

 occasion a' protrusion of the radicle to nearly 

 a-quarter of an inch beyond the grain in niost of 

 the specimens, and in the other of which it had 

 been checked before the radicle was a line in 

 length; the quantity of sugar afforded by the last 

 was to that in the first nearly as six to five. 



The saccharine matter in the cotyledons at the 

 time of their change into seed-leaves, renders 

 them exceedintrly liable to the attacks of insects: 



to which it has been exposed during its deposition 

 from clouds. It is the instinct leading these fish to 

 seek a supply of air for their eggs which carries them 

 from seas or'lakes into the mountain country, which 

 induces them to move against the stream, and to en- 

 deavor to overleap weirs, mill-dams, and cataracts. 



