1902.] 



Influence of Carbon Dioxide on Leaves, etc. 



409 



Appendix. 



Details of the experiments made on Plants in Greenhouse. One set A 

 grown in ordinary air, the other set B grown in air containing 11*47 

 parts of CO^per 10,000. 



For list of these plants, see p. 407. 



The experiment was commenced on May 13. 



(1.) Cucurbita Pepo. 



June 10. — The only difference observable between the two sets of 

 plants, was that a much less number of flower-buds was developing on 

 the plants of set B in air with extra C0 2 . 



June 29. — The development of the flower-buds on the plants grown 

 in extra CO> was now completely arrested. 



July 13. — A well marked difference between the two sets. Those 

 of set A, in ordinary air, had formed flower-buds in all the axils and 

 were flowering luxuriantly. The plants of set B (extra C0 2 ) were 

 much the taller, owing to an increased number of internodes. There 

 was also a considerable tendency to the production of secondary 

 axillary shoots instead of flower-buds, whilst all the flower-buds 

 which had formed had long since fallen off before they were fully 

 developed. 



(2.) Impaiiens platypetala. 



June 10. — All the four plants of set B (extra C0 2 ) were very 

 unhealthy in appearance, having lost nearly all their leaves, and 

 with no vestige of a flower-bud. The controls of set A in ordinary 

 air were very healthy in appearance, and were bearing numerous 

 flowers. (See Plate 5.) 



June 29. — The plants of set B (extra C0 2 ), after losing their leaves, 

 proceeded to shed certain internodal parts of their axes just above a 

 node, and this process was in some cases repeated for some distance 

 down the axis. On this date the plants were showing signs of 

 recovery, and had produced a second crop of small and very dark 

 green leaves. 



The control plants A, in ordinary air, were normal in every way,, 

 and had just finished flowering. 



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

 two sets. Those of set A (ordinary air) were somewhat the taller, 

 the axes being more divergent and the leaves not so closely set. The 

 leaves were also larger and lighter green than those of B. Set B 

 (extra C0 2 ). The plants had now recovered, and acquired a fairly 

 healthy appearance. There were no flower-buds formed, and the 

 leaves (second crop) were much smaller and darker in colour than 

 those of set A. 



