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Dr. J. B. Farmer and Mr. S. E. Chandler. [May 6, 



account of the great diminution in the size of the latter as compared 

 with that of the plant grown under normal conditions, and because 

 the total number of the whole epidermal cells in the smaller leaves 

 may also be smaller than that of the epidermis of a normal leaf. 



4. The anatomical structure of the internal tissue of the leaves is 

 not materially altered, any modification that may arise consisting 

 chiefly in the relative number of cell layers, and of the abundance of 

 intercellular spaces formed. 



5. The anatomical structure of the stem commonly differs in the 

 direction of the formation of less lignified elements of the xylem, a 

 smaller number of vessels, and frequently also in the imperfect de- 

 velopment of the mechanical tissues. The phloem, on the other hand, 

 shows no alteration. The change in the xylem is almost certainly^ 

 related with the diminished leaf surface, and consequently reduced 

 transpiration. But bearing in mind the stomatal relations mentioned 

 under 3, it is probable that the reduction is also connected with dis- 

 turbances of the metabolic processes which may act, not only in the* 

 way here indicated, but also may more directly affect the means of 1 

 supplying material for the growth in thickness of the cell walls. 



6. The last point is emphasised by the invariable accumulation 

 (except in Kalanehoe, and it will be remembered that the metabolic 

 processes of succulent plants are frequently peculiar) of starch in the 

 leaves and ground parenchyma of the treated plants. As regards 

 Kalanehoe, the guard cells of the stomata, which are in many respect* 

 comparatively isolated from the other tissues, do contain more starch 

 in the treated than in the normal plants. It is also worth noting that 

 in this plant the tannin so characteristic of the specimens grown under 

 normal conditions is very much reduced in the experimental series, a 

 fact which further points to a disturbance of the ordinary course of 

 metabolism. 



7. No alteration could be detected in the roots as a consequence of 

 the increase in the carbon dioxide contents of the atmosphere. 



8. When crystals of calcium oxalate occurred in a species they were 

 always less abundant in the treated than in the control plants, with 

 the possible exception of Fuchsia. 



It remains to be stated that the results here described apparently 

 differ in a remarkable way from those obtained by Teodoresco,* who 

 investigated the action of increased carbon dioxide upon growth. The 

 conditions of the experiment, however, in the two cases were by no 

 means similar. Teodoresco compared plants which had been grown 

 in an atmosphere entirely purified from carbon dioxide with others 

 grown in air containing an amount varying from 1*5 per cent, to 2 per 

 cent, of this gas. He found that under these conditions, the plants 



* E. C. Teodoresco, " Influence del'Acide Carbonique sur la Forme et la Struc- 

 ture des Plantes," ' Eev. Gren. de Botanique,' vol. 11, 1899. 



