Wounded Plants. 
539 
Care must be taken, however, or portions of the corky 
layer which heals the wound will come off, and the fresh 
surfaces thus laid bare cause an increase in respiration. 
During the night-time, or other times when determinations 
were not being made, the receivers containing the plants were 
placed in an inverted position to allow for the escape of the 
C0 2 formed ; or, as was more often the case, connected with 
the aspirator, so that no abnormal conditions could occur 
owing to the lack of 0 9 or the accumulation of C0 2 in the 
receivers. Throughout the course of the experiments the 
plants used were kept well supplied with moisture to keep 
them turgid, but no excess of water was allowed to stand in 
the receiver. A careful watch was kept for the growth of 
Fungi or Bacteria on the plants, but no difficulty was ex- 
perienced from this cause, even in the experiments which 
were continued for a week or more. 
Discussion of Results. 
Concerning the ordinary course of the respiratory activity 
of an injured plant, it may be said in general that there is an 
increase, varying very much in point of time and extent with 
the character of the plant and the conditions to which it is 
subjected, followed by a subsequent decrease to the normal 
or almost normal respiration as the wound heals. Reference 
to any of the experiments will afford evidence of this ; for it 
will be seen that an increase of more than ioo per cent, was 
often found during the period of maximum respiration. In the 
case of potatoes, carrots, and other bulky tissues, it will be 
observed that in almost every case there is, during the first two 
hours, a very sudden and marked increase, which, however, falls 
again rapidly, although to a point still considerably above the 
normal respiration, to rise more slowly later to the maximum 
production of C0 2 . The causes of the first sudden increase 
will be discussed later ; at present the general effect of the 
injury demands attention. The respiratory activity in these 
plants is at its height on the beginning of the second day, or 
O o 2 
