182 NATURAL SCIENCE [September 



operations which take place in the leaf are of a comparatively simple 

 character. Before, however, we proceed further, it will be advisable 

 and indeed highly requisite to provide a table after Mesnard (slightly 

 altered) : — 



Products of assimilation. Products of de-assimilation. 



Free fatty oil. Tannoid compounds (rutin, etc.). 



Carbohydrates (starch, glucose, Resins, balsams, and essential oils. 



etc.). Tannins. 



Albuminoid matters of reserve. Coloured pigments. 



It would be superfluous to adduce facts as bases for arguments 

 to prove that the sketch here set forth is a positive and veritable 

 representation of what actually comes to pass in the chemistry of 

 the living foliar organ. No one disputes that fats, carbohydrates, 

 and albuminoids are direct products of assimilation. The fat oil is 

 deposited in the cells without there being a simultaneous deposit of 

 albuminoid matters ; but that there is some close connection 

 between the oil and the starch and sugar is evident (though only 

 provisionally and superficially) from the respective distribution of 

 these bodies in the plant tissues. Thus the oil of the ripe seed is, 

 according to Sachs, produced from the starch and sugar transported 

 from the primary stem. The storing up of oil occurs in all the 

 amylaceous tissues. In the autumn the starch contained in the 

 branches of our forest trees is gradually ' transformed ' into oil, and 

 in the spring this oil is again ' transformed ' into starch and sugar. 

 The cells of the leaf which are free from oil are also free from 

 starch. On the other hand, the fact that oil occurs stored up in 

 the cells of the perisperms or of the cotyledons of certain seeds in 

 Cruciferae, poppies, flax, almonds, etc., in which little or no starch 

 is produced, would seem to show that oil and starch are more or less 

 independent of each other. " In all cases," says Mr Mesnard, " the 

 fatty oil is independent of the starch and the glucose, even in the 

 rare cases of grass seeds where the oil is specially localised." I 

 think it by no means follows because, as in the winter boughs of our 

 forest trees, the oil steps into the place of the vanishing starch, and 

 vice versa in the spring, that therefore one of these bodies is un- 

 questionably derived from, transmuted into, or even formed at the 

 expense of the other. Protoplasmic activity specifically directed is 

 amply capable of creating or of destroying one or the other con- 

 stituent independently and in accordance with the contemporary 

 needs of the organism. Possibly may it not be that the winter 

 production of oil is associated with low vitality, while the summer 

 production of starch is associated with a high vitality? With regard 

 to the organic acids of the leaf, I adhere to the views of Deherain 

 and others that they are oxidation products of the carbo-hydrates, 

 and have got nothing to do with the synthesis of the proteids. 



