on the Growth of Barley and Wheat in Water Cultures . 81 
jram 5 
development, and were nearly as dark in colour when harvested, but some 
of the lowest leaves had begun to turn yellow, ‘ and a trace of red was visible 
in the stem a few days before cutting. In N/10-plants these phenomena 
were more marked. The withering of the lower leaves and coloration 
of the stem had set in at an earlier date and were more pronounced, also the 
general development was less good. With the lowest concentration (N/20) 
the shoots were very much smaller than in any of the others, and were 
of a yellowish green colour, while the lowest leaves had died off a fortnight 
earlier, at the same time as the red colour appeared in the stems. 
The general trend of these observations is reflected in the dry weights 
of the plants, which will be discussed later. 
Sohitions never changed . The difference in concentration affected 
root growth immediately, each strength of solution having a definite effect 
of its own. The N/5-roots fell 
behind the normal within a 
week, being short and rather 
bushy with laterals standing 
out from the rootlets at an 
angle. These laterals elongated 
later, and gave the roots a more 
typical appearance till they 
looked stronger than the N, 
but this appearance was falsi- 
fied by the dry weights. In 
the lower concentrations the 
roots were very poor at first, 
bunchy, with rather thick late- 
rals standing out on every 
side, giving the roots a ‘ stark * 
appearance, but later on de- 
velopment became more normal in type, though still weak. The abnormal 
development of thick unbranched rootlets seen with ‘ frequently changed ’ 
plants was not noticed in any instance where the solution remained un- 
changed throughout the course of the experiment. Shoot growth showed 
a regular depreciation as the concentration of the nutrient solution diminished. 
The weaker the solution, the earlier etiolation set in, and the sooner did the 
lower leaves begin to die off and the red colour appear at the base of 
the stem. Towards the close of the experiment the difference in the 
amounts of water lost by transpiration was very marked, hardly any being 
given off by the N/20-plants. 
Sohitions once changed . The single change of solution kept the 
N-plants growing better, so that at harvest-time the plants were more 
strongly developed and of better colour than in the ‘ never changed ’ set, 
G 
Curve i. Mean dry weights of ten barley-plants 
growing in nutrient solutions of different concentra- 
tions. Dotted lines show the limits of probable error. 
F, frequently changed ; O, once changed ; N, never 
changed. (March 15-May 3.) 
