1902.] 



Influence of Carbon Dioxide on Leaves, etc. 



411 



(6.) Solanum atrojmrpureum. 



June 10. — The leaves of set B (extra C0 2 ) were somewhat curved 

 downwards, and the axes were distinctly higher than those of the 

 controls. The spines on the leaves and stems were not so fully 

 developed as on the control plants in ordinary air. (See Plate 8.) 



June 29. — It was very remarkable to note how the axis of each 

 plant of set B (extra C0 2 ) had become elongated as compared with 

 the controls. There was also a less marked development of spines in 

 the former case. 



July 13. — There was now a very marked difference between the 

 habits of the two sets. Without exception the plants of set B (grown 

 in extra CO2) were much taller. The height of the three plants in 

 extra C0 2 was found to be from 23 to 24 inches, and the number of 

 internodes 23 to 24, the average length of the internodes, therefore, 

 being about 1 inch. In set A, grown in normal air, the height was 

 about 14 inches, and the number of internodes about 16 ; so that 

 the average length of the internodes in this latter case was about 

 0*8 inch. There were more internodes on the plants grown in extra 

 C0 2 , and they were somewhat longer. 



There were about twice as many leaves on the plants grown in 

 ordinary air, and the spinous hairs were more closely crowded together 

 on these control plants, were stronger in growth, and of a deeper purple 

 colour. No flowers had been developed on the plants of set B, grown 

 in extra C0 2 . 



(7.) Kalanchoe Welwitschii. 



June 10. — The control plants of set A in ordinary air were the 

 better grown, and possessed larger leaves than those of set B (extra 

 C0 2 ). 



June 29. — There was but little difference in the height of the two 

 sets, but the contrast as regards the size of the leaves was still very 

 marked. 



July 13. — The differences in the direction already indicated were 

 still more pronounced. 



(8.) Fuchsia. — (a) Variety with Lighter Leaves. 



June 10. — The plants of series B, grown with extra C0 2 , were not 

 quite so tall as the controls, and their leaves were smaller. The 

 flower-buds of this set commenced to develop, but soon dropped off 

 after becoming very green. 



June 29. — The habit of the plants grown in extra C0 2 was a little 

 denser than that of the controls. Whilst the controls (in ordinary 

 air) were flowering copiously, the flower-buds of set B (in extra C0 2 ) 

 became green and were shed before they opened. 



VOL. LXX. 2 F 



