1921] 
MEIER—ROOT TIP 
129 
In determining the time factor, the current was kept at constant 
amperage by sliding resistances for a definite time period, the time 
being measured by a stop watch. The usual practice was to treat 
seedlings in succession in the same manner (as to time and current), 
TABLE VII 
CURRENT 0.I MILLIAMPERE, 40 VOLTS; CRITICAL TIME 9 MINUTES 
5 Average 
Number | Directi ime of}, Number Dees 
Lot number | of roots | of | *Posure |'rain(4)'| showing | above Parent 
sed. current aieuniia yp curvature only alas 
Se en eae 5 420 0.6 s 5 ° 
ft op os Spee acer Io 480 —o.2 I 6 4 
4 LOTT Rea eae aiecal II 480 —o.2 ° 7 4 
A ats, 8 \ 510 —0.7 ° z 7 
VE 3s tee ere 9 525 —0.4 I 2 7 
a Re” Seater 13 550 —0.5 ° 2 II 
10, 14, 19, 22 20 540 =O.4 ° I 19 
Se aes ah oe 5 570 gio & ° 2° 5 
Se et 9 600 —0.6 ° ° 9 
co Ee Io . 600 ~—0.7 ° ° id 
TABLE VIII 
CURRENT 0.05 MILLIAMPERE, 30 VOLTS; CRITICAL TIME PROBABLY BETWEEN 32 AND 
35 MINUTES 
Number | Direction | Time of hae Number | Dead 
Lot number of roots of xP’ | gain (+) | showing | above net 
used current | iinutes | 2 — curvature} only also 
eee Sig Oe May 3 15 —0.5 ° 3 4 
Ret + 18 —o.2 ° I ° 
eg ae ne: 7 1 25 —0.2 ° 3 * 
Wee 5 \ 28 —o.r t * 4 
eens 16 30 —0.3 3 3 13 
oO niet Spe es OS 6 32 —0.4 I T 5 
Bie ee 2 35 —0.5 ° sid , 
Sa en 4 { 35 —0.5 ° ks 4 
CG a gs ah 2 q 40 0.2 ° - . 
ce Re ere 2 h qo. | 0.3 ° ° - 
EONS aS ah eee 2 50 ee ° ° . 
such group (usually five), being designated as a “lot” in the tables. 
Roots were exposed for a time, calculated from preliminary experi- 
ments to be below that required to kill, then time of exposure 
increased for next lot and so on until all were killed. When ninety 
