528 Townsend. — The Correlation of Growth 
(Table XIV, column 3). If a stalk was cut, the reduction 
in growth was greater than when a mycelium was cut 
(Table XIV, column 4). In column 5, Table XIV, the same 
stalk was cut three times. The first time about one-third 
of the stalk was removed, causing a decided retardation in 
growth of another stalk on the same plant. The second and 
third cuttings removed the remaining two-thirds of the same 
stalk, but produced no change in the rate of growth of the 
stalk under observation. 
When a solution of from 3 to 5°/ o of KN 0 3 was applied to 
the mycelia of Phycomyces , the growth of the stalk was 
gradually retarded until it finally ceased. If the turgor was 
restored by displacing the KN 0 3 solution with water, the 
growth began again in from twenty to sixty minutes. The 
length of time required for the resumption of growth 
depended upon the strength of the KN 0 3 solution used, and 
upon the time during which the growth had ceased. Cross- 
walls formed in the mycelia in from one to two hours after 
cutting, while the return to the normal rate of growth usually 
took place in from thirty to sixty minutes ; hence it is clear 
that the formation of cross-walls could not have influenced 
the return to the normal rate of growth. 
Conclusions. 
Distance through which the irritation acted 1 . When 
nearly the entire root of seedlings was removed, the point 
of injury was only from one to ten millimeters from the 
lowest point of the growing-zone of the shoot. Likewise 
when the leaf-tips were removed (as in Table V), or a leaf 
was cut from the growing shoot (as in Table VI), the 
shortest distance to the zone of growth did not exceed a few 
millimeters. On the other hand, if the root-tip alone was 
removed or split, the irritation had to act through nearly the 
1 Rothert, Ueber Heliotropismus ; Cohn’s Beitrage zur Biologie der Pflanzen, 
Vol. vii, p. 66, 1896. 
