26 BOARD OF AGRICULTURE. [Jan. 



Professor Whitcher. I do not think there would be 

 very much of a point there, from the foot that plants do not 

 take up carbonic acid through their roots ; the carbonic acid 

 of the plant is taken in through the leaves, and comes 

 from the atmosphere ; and, while the amount of carbonic 

 acid in the atmosphere is very small, nevertheless it is always 

 amply sufficient to supply the amount that is required for the 

 growth of large crops. In other words, if Ave furnish every- 

 thing else that the plant needs, the plant will take care of 

 itself, so far as obtaining a sufficient quantity of carbonic 

 acid. 



Mr. Hersey. What amount of carbonic acid do plants 

 require ? 



Professor Whitcher. There have been a good many 

 experiments made, showing different percentages ; but, if I 

 remember correctly, there has been no advantage shown in 

 increasing the amount above that contained in the atmos- 

 phere. 



Mr. Hersey. Is there not some German authority who 

 tells us that plants grow best in eleven per cent of carbonic 

 acid gas ? 



Professor Whitcher. Eleven per cent would be a 

 pretty heavy dose of earbonic aeid, and would prove injuri- 

 ous to most plants. 



Mr. Hersey. I know it would be ; but, as the result of 

 some experiment that was tried, it was stated that common 

 soil contained from 37 to 125 parts in 10,000, but that well- 

 manured soil after a heavy rain, in warm weather, contained 

 1,300 parts of carbonic acid gas. I think it is well to bring 

 this up, because I think it is one of the things that the 

 experiment station should take hold of and ascertain beyond 

 the possibility of doubt whether we are losing anything by 

 losing the carbonic acid gas from our manures or not, and 

 whether the common air has enough for the excessive 

 growth of plants which we require. I have no doubt that 

 there is carbonic acid gas enough in the common air for the 

 growth of forests ; but I very much doubt whether the aver- 

 age amount is sufficient for the growth which we demand in 

 our gardens. 



Professor Whitcher. I would like to say, in connection 



