1907] JENSEN—TOXIC LIMITS AND STIMULATION I5 
That it is next to impossible to coordinate data from different 
authors is evident from Table B, taken from CAMERON and Brea- 
ZEALE (7). For, as they say, the toxicity needed “to kill a seedling 
or disorganize an entire radicle varies widely from that required 
to completely hinder any growth, or that which will permit some 
elongation.” 
TABLE B 
| Toxic Lints For 
SoLUTE 
| Whole seedling | Tip of radicle 
lg iGiges dekh hon er etes n/9Q n/ 15000 
Mee Re are n/1o n/ 18000 
PRIN ic rides cniioh oc Bes n/7 n/ 5000 
PRIS GT 5 lors s hes n/%3 fa 
aloes) n/t n/ 15000 
SUCCUME ACId). 2 3:6. n/t n/ 20000 
Calci hlorid: . 6... n/3 n/ 
Calcium nitrate...... n/3 n/§ 
DANDENO (11) worked with pea, lupine, and corn. He found 
that the toxicity of poisonous solutions is reduced by the presence of 
pure quartz sand. Thus in CuSO,, seedlings will grow in 2/4096 
when sand is present, while they will stand only /32768 when no 
sand is present. He also found that the effect is related to the size 
of the particles, more growth being permitted with fine sand thaa 
with coarse sand. My own experimentation with H,SO, shows 
similar results. Thus with number 5/o, the finest quartz, growth 
Was inhibited at 7n/1t0oo to 6n/100o; in number 2/o, the next 
coarser grade, at 52/100 to 42/100; in number 2, a rather coarse 
sand, at 42/100 to 2n/100; in number 4, a very coarse grade, at 21/100 
to 9/1000; in solution (H,O), at 82/1000 to 6n/r1000. Which goes 
to show that the coarser the sand the less the same amount of solution 
is reduced in toxicity. Or, in other words, the coarser the sand, 
the nearer does the culture approach to solution media. DANDENO 
does not think with TRUE that the growth of lateral roots in solutions 
that killed the primary radicle is due to “accommodation,” but 
that the first growth of the radicle has reduced the toxicity to such an 
extent that the later roots can endure it. That the quantity of toxic 
agent has considerable to do with the effect upon growth, he shows 
