Growth Studies. 
I. A Quantitative Study of the Growth of Roots. 
BY 
J. H. PRIESTLEY and A. F. C. H. EVERS H ED. 
With five Tables and six Figures in the Text. 
Contents. 
PAGE 
1. Introduction 224 
2. Experimental Material and Methods 225 
3. Experimental Results 226 
4. Interpretation of Experimental Results 233 
5. The Sachs ‘Grand Period’ of Growth *. 235 
6 . Summary * 236 
7. References . 236 
1. Introduction. 
D URING the last few years an extensive re-exploration of the problem 
of growth has taken place in which quantitative methods have been 
widely employed. We shall not attempt any summary of this work, as the 
present state of our knowledge has recently been presented very fully, 
especially in a series of papers by Briggs, Kidd, and West (3 and 11). 
Modern quantitative studies of plant growth are mainly based upon 
data as to changes in volume or length, whilst animal physiologists measure 
the growth of animals in terms of increase or decrease in length. This 
difference in attack is simply determined by the nature of the experimental 
material. Any investigator who has made efforts to record the growth of a 
baby or any other active young animal will know that length measurements 
demand a more than expert manipulation. On the other hand, if plant 
weights are to be significant, they must be dry weight determinations, and 
then the possibility of the progressive record of the growth of the same 
individual plant is removed. 
Quantitative work upon the growth of animals appears to have been 
more fruitful in interpretation, and the reason seems to be that the records 
are of increase in mass and not in area or length. With the plant, change 
[Annals of Botany, Vol. XXXVI. No. CXLII. April, 1922.] 
