206 
C. West , G. E. Briggs , rmd F. Fidd. 
the relations it is proposed to record at weekly intervals 
throughout the life of a plant do not involve any general 
presumptions as to the factors controlling growth as a whole, such, 
for example, as the presumption that growth is controlled by 
assimilation or that growth is controlled by root absorption. Our 
attitude is that general conclusions should be postponed until 
sufficient secondary data, based on sound primary data, have been 
carefully analysed. From the primary data mentioned above 
other secondary data in addition to those proposed by us can 
obviously be obtained, and as analysis proceeds it is possible that 
some of such further relations may be found to be significant in 
finally arriving at conclusions with regard to the various factors 
controlling growth. 
The quantitative analysis of plant growth week by week 
by some such method as that outlined has not been carried out 
before, and we have been influenced in putting forward our 
tentative suggestions by the hope that they will stimulate and be 
of use in further research. It is obvious that it would be a distinct 
advantage if various workers on this problem would make use of 
the same general methods or at least present their results not only 
in graphical form but also by giving the actual figures obtained. 
It is much to be regretted that such a contribution to the subject 
as that of Brenchley (3) is devoid of any primary data whatever 
concerning the plants themselves. 
Botany School, Cambridge. June , 1920 . 
NOTE, 
In reply to a suggestion put forward by us in the previous 
number of this journal (6) to the effect that from an economic point 
of view the “ substanzquotient” is preferable to the “efficiency 
index” in that it only states the ratio of final weight to seed weight 
divided by time and makes no assumption as to the rate of 
addition of dry material, Professor V. H. Blackman (2, p. 99) 
states that “ a formula in which final weight is divided by seed 
weight and by time implies that there is a linear relation between 
time and weight.” This would have been the case if we had said 
that the “ substanzquotient ” was a constant, but we stressed the 
point that the “ substanzquotient” varied with time and hence had 
no physiological significance. 
