REPORT OF THE CHEMIST. 59 



Pasteur, aud the views of the latter are supported by Struve, who, in 

 the course of an investigation of the gases found in fruits, placed some 

 grapes under water, free from air, under conditions favorable to exhaus- 

 tion of air, and at the close of the experiment found that the water con- 

 tained small quantities of alcohol and yeast-cells, but on careful exam- 

 ination of the grapes was unable to find any yeast-cells in their interior. 

 The reliability of Fremy's conclusions are therefore questionable. 



As might be inferred from the presence of alcohol found in plants and 

 fruits, the gas they contain generally consists of carbonic acid. Thus 

 Struve has found that when grape-leaves are covered with ether, a lib- 

 eration of gas takes place, varying in amount with the stage of their 

 development, being most abundant in young leaves. Grapes similarly 

 treated give off no gases, but do so when covered with water and placed 

 under a bell jar from which the air is subsequently exhausted by means 

 of the pump. The gas liberated was found in each case to consist en- 

 tirely of carbonic acid. 



On analysis of the gas contained in tho pod of Colutea arhorescens, 

 (bladder-nut,) Bender found it to consist of 2.3 carbonic a.cid, 18.7 per 

 cent, of oxygen, and 79,1 per cent, of nitrogen. These results correspond 

 closely with those obtained by Saintpierre and Magnien, who find, how- 

 ever, that these proportions vary, not only with the time of the season, 

 but also with the time of the day in which the pods were collected. 

 Bender considers that the gas is obtained entirely from external sources 

 by transfusion through the walls of the pods ; but the results of the ex- 

 periments of Saintpierre and Magnien seem to favor their view, that the 

 carbonic acid is due to internal exhalation, and that it subsequently 

 becomes mixed with atmospheric air by transfusion, in accordance with 

 the law of diffusion of gas ; that the oxygen of the air thus taken in is 

 absorbed by the green j)ods in the process of growth. A simultaneous 

 liberation of carbonic acid taking place, the latter being often greater 

 than the absorption of oxygen, and producing distension of the cell- 

 walls of the pod. But it must not be inferred from the results just 

 described that the gases liberated by plants always consist of carbonic 

 acid ; for Joseph Boehm has observed that when branches of woody 

 plants were placed in direct sunlight under water freed from air by boil- 

 ing, a liberation of gases immediately began, and in a short time there 

 was set free an amount greater in volume than that of the twigs under 

 experiment. The last i)ortions were almost pure oxygen. Though he 

 considers this a physiological phenomenon, he does not, for the present, 

 attempt to explain it ; but Ad. Mayer, who has also observed the phe- 

 nomenon, considers it due to the formation of starch under the influence 

 of light, by reduction of acids which have been formed by oxidation of 

 starch in the absence of light. The results of other investigations, as 

 will appear further on, suggest the idea that there may be in such case an 

 oxidation of sugar, siuce it has been shown by different persons to exist 

 in leaves in considerable quantity. Thus Deherain has detected its 

 presence in the leaves of beets, and from the results of the investigations 

 of Corenwinder it appears to be located principally in the ribs or veins, 

 and that in these parts it amounts to 1.607 per cent. From further ex- 

 periments he has found the percentage higher in roots having large, 

 well-developed leaves than in those having smaller ones. Joseph 

 Boussingault has also found sugar in the petals of certain flowers, and 

 has estimated the amount present. He divides tho sugar found into 

 reducible sugar and invertible sugar. The first may consist of inverted 

 sugar, glucose, levulose, or even inactive sugar, or, what is more prob- 

 able, a mixture of them all, having the power to reduce cupric oxide. 



