94 Franklin Kidd , Cyril West and G . E . Briggs 
the indication seems to be that the reason for terminating the 
experiment was completion of growth, not weather conditions. An 
inspection of this column will show that H. cucumevifolius nanus , 
which for all previous periods had a considerably lower average 
efficiency index, now has one as high as that of H . arboveus 
giganteus and actually larger than that of H. macrophyllus giganteus 
and that of H. uniflorus giganteus. Column 6 gives the efficiency 
index for thej periods during which it is at a maximum and 
approximately constant for each species. It should be noted that 
the length of this period varies considerably. Finally, the 
last column gives the ratio of final weight to seedling weight, which 
after all is the value of most importance economically. A 
consideration of the variations in the relative values of r will show 
how misleading it is to state from an inspection of column 6 alone, 
as Blackman does, that H . cucumerfolius nanus has a lower efficiency 
and that the dwarfness of this plant is due to this lower efficiency 
as well as to its smaller seed. It certainly has a lower efficiency 
when compared with the other four species over these periods, but 
when compared over the whole life-cycle it has a higher economy 
of working than two of the other species. 
Again, it is obviously misleading to compare two plants over 
different portions of the life-cycle for each. For example, for the 
period of fifty-six days H. cucumevifolius nanus has an average 
efficiency index of 10*6 whereas H . nanus for a period of ninety 
days has an average efficiency index of 9*1, thus indicating that the 
former has a greater economy of working : whereas comparisons 
for any equal period for the two plants or for the complete life- 
cycle show that H. nanus has the greater average economy of 
working. 
Brenchley’s Application of the Compound Interest Law. 
In Brenchley’s work two series of experiments, with mustard 
and barley respectively, were carried out to find the effect of 
competition upon plant yield. For this purpose a varying number 
of plants were grown per pot. The seeds were sown in double 
quantity and at germination were thinned out to the number per pot 
required. In the case of mustard (species not given) the plants 
were harvested after 59 days, in the case of barley after 117 days. 
In the case of mustard at the time of harvesting “ a definite 
gradation of maturity occurred according to the number of plants 
in the pot. The single plants (per pot) were very strong, sappy, 
exceedingly tall and decidedly less mature than any others. . * . . In 
