250 LOCK : THIS GROWTH OF 
a fairly large surface of transpiring leaves, whereas in the 
early stages of growth its own transpiration must be very 
Growth during the day was almost always considerably 
slower than at night. On a single occasion only was a greater 
hourly growth recorded for the period from 7 A.M. to 5 P.M. 
than for the following period from 5 p.M. to 7 A.M. On this 
occasion rain fell continuously during the whole of the day, 
and in consequence of this the psychrometric condition of 
the air closely approached saturation, and the day therefore 
equalled in moisture, or possibly even exceeded the following 
night. 
Observations taken hourly showed a very regular periodicity 
of growth during the 24 hours. During the night growth 
was rapid and, as far as errors of observation allowed of 
judging, nearly constant. Soon after sunrise the growth fell 
off rapidly and, during the day, was on the whole low, rising 
again shortly before sunset. 
During a considerable series of days measurements of 
several halms were made every two hours. The majority of 
these I have not found space to record, and they were in 
many ways incomplete. But they showed quite clearly, and 
without any actual psychrometric records, the marked 
relationship between growth and meteorological conditions.' 
In bright sunshine elongation was always slow or even 
ceased altogether, and sometimes an actual shrinkage 
was observed. When clouds gathered growth increased, and 
when rain was falling it was still more rapid. On several 
occasions the morning was sunny, the middle of the day over¬ 
cast,and the afternoon again bright. And on such days the 
rate of growth always rose towards noon whether rain actu¬ 
ally fell or not, and this rise was often followed by a falling 
off later on. 
Experiments made by covering up young growing culms 
seemed to show that the effect of light upon these had very 
