2o6 LOCK : THE GROWTH OP 
Of the experiments which have been carried out in this 
direction, by far the greater number have consisted in 
exposing the growing cells to the direct action of saline 
solutions according to the method introduced by H. de Vries.* 
Observations of this kind have established the important 
part played by turgour in the process of elongation, but they 
can give little information as to the sensitive reaction of the 
growing regions of the plant to changes of moisture, owing to 
the essentially abnormal conditions under which such 
experiments are made. Moreover, except in the case of 
de Vries’ own experiments, which were concerned chiefly 
with the determination of the length of the growing region 
in a variety of cases, the number of plants which have been 
tested in this way is very limited. For several workers the 
roots of Vicia faba have provided the sole object of study. 
There is no need to dwell further on this class of 
experiments. Reference may next be made to the principal 
papers in which the question of the effect of atmospheric 
moisture upon the growth of internodes is dealt with. 
Sachs in his well-known paper dealing with the effect of 
temperature and light upon the growth of intemodesf quotes 
observations made by W. H. de Vries upon the flowering 
scape of Agavea mericana in 1847. During the period from 
August 9 to September 1, measurements showed that on five 
slight shrinking, and during two 
mornings, both of which were dull, there was a slight 
elongation. Some of the observations upon Dendrocalamus 
recorded above closely recall these measurements of de 
Vries upon Agave. 
Sachs himself made no experiments upon the effect of 
moisture. He took peychrometric observations during his 
experiments, but kept his wet and dry thermometers standing 
t Arbeiten d. Bot. Inst, in Wurzburg, II., p. 1 
