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



(2.) The average relative areas of the leaves. 



In order to obtain this estimate the leaves were traced on paper, 

 the pattern then cut out, and the average weights of each series 

 obtained. 



(3.) The number of stomata per unit of area of leaf surface, and also 

 the relative number of stomata and epidermal cells per unit area. The 

 object of the latter determination is to endeavour to ascertain whether 

 any observed alteration in the total number of stomata per unit of 

 area should be ascribed to an alteration in the degree of development 

 reached by the epidermal cells, or whether it is to be referred to a direct 

 increase or decrease of the stomata as the result of the influence of the 

 added carbon dioxide. 



(4.) The anatomical differences in the stems and leaves. 



(5.) The relative amount of starch and other cell-contents in the two 

 series. 



The drawings which illustrate this communication are all drawn 

 carefully to one scale, and are therefore strictly comparable for purposes 

 of measurement. 



Kalancho'e Welwitschii. — The average length of the four youngest 

 internodes in the air plant as compared with those of the COo plant is 

 in the proportion of l'O : 0*75, taking those of the air plant as unity. 

 If the development of the internodes in the two series be traced back- 

 wards, it is found that the C0 2 plant attains to its final internodal 

 length sooner than does the air plant. Thus in one example, whilst 

 the full length was reached in the C0 2 plant at the third or fourth 

 internode, it was not till the fifth that further extension ceases in the 

 air plant. The effect of this is to further emphasise the stunted 

 appearance characteristic of the C0 2 series. 



The leaves differ greatly in the two sets, being larger (1*0 : 0*17), 

 thicker (1*0 : 0*7), and more broadly ovate and serrate in the air-grown 

 specimens. As regards the stomata, the guard cells were of approxi- 

 mately equal size in both series, but were always widely opened in the 

 CO2 plants, whilst they were closed in the control. This points to a 

 permanent alteration of form, seeing that the material throughout was 

 already killed and preserved in spirit. A similar difference in the 

 appearance of the guard cells we found to be very constantly exhibited 

 by all the other species examined by us. 



The numerical proportion of the stomata in the two series per unit 

 of leaf (under) surface was about 1*0 : 1 '5 (fig. 1, A and B); but this 

 is largely due to the decreased size of the rest of the epidermal 

 cells in the plant treated with carbon dioxide. This is proved 

 by ascertaining the ratios between the number of epidermal cells and 

 stomata in the two series respectively ; it is found to be lOO'O : 7*3 for 

 the air plant and 100*0 : 7-1 for the C0 2 specimen. It thus appears 

 that in Kalancho'e there is no material disturbance of the normal 



