80 Brenchley. — Effect of Concentration of the Nutrient Solution 
sponding in strength to that from which the plant was taken, so that 
no check was caused, either by slight desiccation or by shock from the roots 
being laid in pure water or in an alien solution. Each test ran for seven 
weeks, and was repeated three times at intervals of three weeks, so that 
information was obtained for plants grown early and late in the season. The 
developmental history was carefully noted, and it was found that the differ- 
ence in growth of plants in different concentrations was not only shown 
by the ultimate dry weights, but was apparent to the eye through the whole 
course of the experiments, both with regard to the size of plants and type of 
growth, especially with the roots. Each plant was harvested separately, and 
the dry weights of roots and shoots recorded. 
First Series. 
Seeds sown, March 5. 
Plants put into solutions, March 15. 
Plants harvested, May 3. 
Solutions changed ‘ frequently \ at regular intervals of four days. 
Solutions changed ‘ once on April 8. 
Solutions frequently changed. Most of the plants started off with 
fairly normal root growth, but the N/20 1 began to vary within the first few 
days, remaining short, with short thin laterals, which gave the roots a square 
bunchy appearance compared to the usual long type. This ‘ bunchiness * 
persisted for several weeks, but eventually the laterals elongated more 
normally. An unusual feature of the root growth was seen in all concentra- 
tions at the end of about a month. In addition to the usual thin roots 
supplied with long thin laterals, there appeared a number of very thick long 
rootlets springing from the base of the plant, either entirely free from laterals 
or else furnished with a very few tiny ones. These rootlets were thickest 
and most numerous in the N-plants and persisted to the end, so that 
at harvest-time the roots were inclined to be thick and much less fibrous 
than usual. In the lower concentrations these roots were very prominent 
at the time of formation, but were overshadowed later on by the further 
development of fibrous rootlets, and at harvest the roots had regained a more 
normal type. 
The development of the shoots in the plants growing in the different 
concentrations was very similar for some long time, but gradually a falling 
off was noticed with the two lowest (N/10, N/20), and by harvest-time some 
indications of this appeared even with N/5 shoots. In the N-plants the 
shoots were of an exceptionally dark green colour to the very end, the 
lowest leaves remained green and healthy, and there was no sign of red 
coloration at the base of the stem. The N/5-plants showed similar 
1 For convenience of reference, the plants in the different concentrations will be called N, N/g, 
N/10, N/20 plants. 
