194 
Smith and Butler . — Relation of 
jar being considered a unit. Thirty- five plants were grown in each of 
solutions A and B, while twenty plants only were grown in solution C. 
The jars confining the solutions were alternately arranged so as to com- 
pensate for all differences in growth that might result from irregularities in 
the environment. Wet sawdust was packed around the jars and brought 
nearly to a level with the tops in order to prevent undue variations of 
temperature in the solutions and keep the roots in quasi-darkness. 
Ten days after the seedlings were placed in the solutions the effect of 
absence of potassium on growth was already well marked. The leaves of 
the plants in solution B were drying up at v the tips, and small crinkled areas 
were distributed irregularly on the older leaves ; while the plants in solu- 
tions A and C were growing nicely and showed no pathognomonic 
symptoms whatsoever. After sixteen days the plants in the full nutritive 
solutions began stooling, while the plants growing in the absence of 
potassium had ceased developing. There was no evidence of stooling and 
all the leaves were drying up from the tips, the older showing in addition 
promiscuous dead and dying areas in other portions of the blade. There 
was no apparent effect upon the chlorophyll due to the absence of potas- 
sium, the death of the tissues not being accompanied by any progressive 
change of colour. 
After twenty-one days the plants in the full nutritive solutions appeared 
to be alike in all particulars ; they were healthy and growing vigorously. 
The plants possessed on the average three stems and a well-developed, 
glistening, white, fibrillose root system. The plants growing in solution B 
had, on the other hand, evidently ceased all development ; the leaves were 
all withering from the tips, the older leaves showing, as on the sixteenth 
day, dead and dying areas scatteringly distributed over the blade, but 
the plants had become increasingly feeble. The root system was poorly 
developed and the side roots, while numerous, were short and stubby and 
dull white in colour. At the close of the experiment, therefore, the plants 
in solutions A and C show no discernible differences, but the effect of the 
absence of potassium on curtailment of growth was extremely striking. A 
study of the data given in Table V shows that solution C gave substantially 
the same growth as solution A. Hence an addition of calcium greatly 
in excess of that present in solution A does not introduce a disturbing 
factor, and we may confidently assume that the symptoms exhibited 
by the plants grown in the absence of potassium were due to the absence 
of potassium and not to disturbances introduced by the change in the calcium- 
magnesium ratio or as a result of the increased quantity of calcium and 
sulphur offered the plants. The mean dry weight of a plant grown in 
solution A was 0-163 r grm., in solution C 0-1819 grm., a difference of 10-9 
per cent., and this difference is still shown when we consider the growth of 
tops and roots separately, but the relative development of the roots, on the 
