1838] 



FARMERS' REGISTER, 



633 



Fig. 17. 



tlon of the leaf must vary according to the com- 

 position of the sap passing through it, and accord- 

 ing to the nature of the products which are Ibrm- 

 ed from it. When sugar is to be produced, as in 

 early spring at the timp. of the developement of 

 buds and flowers, it is probable that less oxygen 

 will be given off than at the time of the ripening 

 of the seed, when starch, or gums, or oils, are 

 formed ; and the process of ripening the seed 

 usually takes place when the agency of the solar 

 light is most intense. When the acid juices of 

 fruits become saccharine in the natural process of 

 vegetation, more oxygen, there is every reason to 

 believe, must be given off', or newly combined, 

 than at other times; lor, as it was shown in the 

 third lecture, all the vegetable acids contain more 

 oxygen than sugar. It appears probable, that in 

 some cases in which oily and resinous bodies are 

 formed in vegetation, water may be decomposed; 

 its oxygen set free, and its hydrogen absorbed. 



Mr. Berard, of Monipellier, has shown that 

 fruits in ripening convert the oxygen ot the air 

 into carbonic acid ; and that the process oi' ripen- 

 ing may be suspended by the exclusion of the 

 fruit from oxygen gas, and that it will go on again 

 after a certain interval of time. Unripe peaches, 

 plums, and apricots, may be preserved in close 

 bottles, filled with air deprived of oxygen, tor 

 from twenty days to a month ; and pears and ap- 

 ples about three months, when they will after- 

 ward ripen per/ectly by exposure to air. 



I have already mentioned, that some plants 

 produce oxygen in pure water. Dr. Ingenhousz 

 found this to be the case with species of the con- 

 fervse. I have tried the leaves of many plants, 

 particularly those that produce volatile oils. When 

 such leaves are exposed in water saturated wiih 

 oxygen gas, oxygen is given off in the solar light ; 

 but the quantity is very small, and always limited ; 

 nor have I been able to ascertain with certainty 

 whether the vegetative powers of the leaf were 

 concerned in the operation, though it seems pro- 

 bable. I obtained a considerable quantity of oxy- 

 VoL. VI.— SO 



gen in an experiment made fifteen years ago, m 

 which vine leaves were exposed to pure water ; but 

 on repeating the trials often since, (he (|iiaiititiCB 

 have always been very much smaller. I am jirno- 

 rant whet her this diliiBrenceisowingto the [)cculiar 

 state o( the leaves, or to some coniervti! which 

 might have adhered to the vessel, or to odier 

 sources of 110 lacy. 



The most important and most common products 

 of vegetables, mucilage, starch, sugar, and woody 

 fibre, are composed of water, or the elements of 

 water in their due proportion, and charcoal; and 

 these, or some of them, exist in alJ plants: and the 

 decomposition of carbonic acid, and the combina- 

 tion of waterin vegetable structures, are processes 

 which must occur almost universally. 



When glutinous and albuminous substances ex- 

 ist in plants, the azo'e they contain may be sus- 

 pected to be derived from the atmosphere : but no 

 experiments have been made which prove this; 

 they might easily be instituted upon mushrooms 

 and funguses. 



In cases in which buds are formed, or shoots 

 thrown Ibrth from roots, oxygen appears to be 

 uniformly absorbed, as in the germination of seeds. 

 I exposed a email potato, moistened with com- 

 mon water, to 24 cubical inches of atmospherical 

 air, at a temperature of 59". It began to throw 

 forth a shoot on the third day; when it was half 

 an inch long I examined the air ; nearly a cubical 

 inch of oxygen was absorbed, and about three- 

 fourths of a cubical inch of carbonic acid Ibrmed. 

 The juices in a shoot separated from the potato 

 had a sweet taste ; and the absorption of oxygen, 

 and the production of carbonic acid, were proba- 

 bly connected with the conversion of a portion of 

 starch into sugar. When potatoes that have been 

 frozen are thawed, they become sweet; probably 

 oxj'gen is absorbed in this process; if so, the 

 change may be prevented by thawing them out of 

 the contact of air; under water, Ibr instance, that 

 has been recently boiled. 



In the tillering of corn, that is. the production 

 of new stalks round the original plume, there is 

 every reason to believe that oxygen must be ab- 

 sorbed ; fbr the stalk at which the tillering takes 

 place always contains sugar, and the shoots arise 

 ii-om a part deprived of light. The drill husband- 

 ry favors this process ; lor loose earth is thrown 

 by hoing round the stalks; they are preserved 

 from light, and yet supplied with oxygen. I have 

 counted from 40 to 120 stalks produced from a 

 grain of wheat, in a moderately good crop of drill- 

 ed wheat. And we are inlbrmed by Sir Kenelm 

 Digby, in 1660, that there was in the possession of 

 the Fathers of the Christian Doctrine at Paris, a 

 plant of barley, which they, at that time, kept by 

 them as a curiosity, and which consisted of 249 

 stalks springing from one root, or grain ; and in 

 which they counted above 18,000 grains or seeds 

 of barley. 



The great increase which takes place in the 

 transplantation of wheat depends upon the cir- 

 cumstance, that each layer thrown out in tillering 

 may be removed, and treated as a distinct plant. 

 In the Philosophical Transactions, vol. Iviii. pa<;e 

 203, the following statement may be found : Mr. 

 C. Miller, of Cambridge, sowed some wheat on 

 the 2d of June, 1766 ; and on the 8th of August, 

 a plant was taken and separated into 18 parts, 

 and replanted ; these plants were again taken up, 



