508 W. J. V. OSTERHOUT 
the experiments (taken from the report of the Students* Observatory, 
University of California) : 
Mean Relative Mean 
1907 Humidity Temperature 
Sept 88.3 59-0° F. 
Oct 88.7 , 58.0 
Nov 86.8 53.0 
Dec 89.3 49.8 
1908 
Jan 90.1 48.2 
Feb 88.6 46.8 
Mar 85.0 49.9 
April 84.0 54.2 
May 84.0 54.9 
June 85.0 56.7 
July 88.0 58.6 
Aug 88.0 57.8 
Sept 86.0 58.3 
Oct 84.0 55.6 
Nov 90.0 51. 1 
Dec 89.5 44.0 
1909 
Jan 92.0 49.8 
Feb 90.0 48.2 
Mar 88.0 ' 48.1 
April 85.0 54.0 
May 77-0 544 
June 84.0 58.2 
July 80.0 60.2 
The humidity of the air of the laboratory was less than that given in 
the table. 
During the experiment each piece produced several new leaves. 
As may be observed in figure i, these are much below the normal in 
size. The new leaves were formed at the expense of the older ones, 
which gradually died and thus furnished material which was trans- 
ported to the tip of the stem and utilized in new growth. 
The amount of growth is surprising when we consider how little 
material can be stored in the old stem and leaves. The plant shown 
in the photograph weighed at the start 2.1 gm. while at the end of the 
exposure to drought it weighed 0.22 gm. or 10.5 percent of the original 
weight. This loss is somewhat less than the average. In one plant 
