112 BIOLOGY. [Book ii, 



appears under the influence of light, and in its absence re- 

 dissolves. We seize here chemical synthesis in some degree in 

 the very act. 



Assuredly proteic substances are also formed in the chlorophyl- 

 lian cell. Doubtless the phenomenon is less evident here ; but we 

 know that tbe sap reaches the leaves in the state of a fluid still 

 very slightly charged, and that it issues from them as a living 

 liquid in the state of nutriment and blastema. 



We have just said that chemical synthesis, exercised upon the 

 chlorophyllian cell, had probably resulted in a subtraction, an 

 emission of oxygen ; but there are, on the contrary, organic 

 compounds that result from super-oxydation ; these are the 

 vegetal acids. Their molecule contains more oxygen and hydrogen 

 than are required to form water. Oxalic acid, one of the most , 

 frequent, contains three atoms of oxygen to two of carbon 

 (C^O^). In laboratories, it is obtained by oxydizing sugar and 

 fecula with azotic acid. In the plant, it is probably produced by 

 the direct action of oxygen upon the same substances. Oxalic 

 acid, in fact, as well as the ternary, acetic, citric, and malic acids, 

 and so on, is not formed in the . synthetic laboratory of the 

 chlorophyllian cells, but in those parts which are not green, or 

 which are sheltered from the light 



Organic vegetal substances are naturally subject in a high 

 degree to isomerism and instability, like all aggregates of this 

 kind ; they also often undergo metamorphoses during the coui-se 

 of the nutritive process. Their molecular mutations succeed and 

 engender each other. 



The spores, seeds, bulbs, tubers, rhizomas, the vivacious shoots 

 of ligneous plants are in ti-uth nutritive reservoirs, where the 

 organised sap deposits organic substances, utilizable at a later 

 time, either for germination or for nutrition, when the flow of 

 lymphatic sap reappears in spring. These substances are then 

 drawn away, and furnish material's for the development of the 

 folial and floral buds, for the nutrition of the tissues, which could 

 not otherwise obtain aliment, frondation not yet existing ; but 



