td 
28 BOTANICAL GAZETTE [JANUARY 
It is evident that the quartz has a very marked effect in reducing 
the toxic effect of the silver. For example, the death point in soil 
is at a concentration of 3/100 to 
H.O . sa 
2n/100; in solution the death poiat 
- Ay is at 2/10000; this, in comparison 
n/'75000 : i\y1-| with other poisons used, is a con- 
; aN siderable difference. 
j ee Working on the assumption that 
n/25000 tt the great difference in toxicity be- 
rites ; 
Pre emer f- Zz tween soil and water cultures was 
i liicae 6o (of we @©=0seette@ «to absorption of the poison 
a i Ke 120 by the sand particles, a series of 
IG. 17.—Silver nitrate series in ° ais 
e 
solution. Feb. 19-Mar. 4. 1906. cultures, all containing the sam 
strength of solution at first, but a 
varying quantity of quartz, was set up. The set consisted of seven 
500°° bottles. The solution strength used was 52/1000. The 
amounts of solution and quartz sand in each bottle were as 
follows: 
Number I 2 3 6 7 
Solution T50°°  208c¢ 310% 365°¢ 4roce, 455°° 500% 
5/o quartz 62587 6258 soogM 3z75gm aoosm resem 258m 
That is, we have in 1 about 19 per ceat. solution to 81 per cent. sand; 
in 2, 25 per cent. to 75 per cent, sand; in 3, 38 per cent. to 62 per cent. 
sand or supersaturated; in 4 the solution stands about 2°™ above 
the sand; in 7 the sand stands less than 1°™ from the bottom; 5 and 
6 are intermediate between 4 and 7. The experiment lasted ten 
days and the results obtained are as follows: 
TABLE VIII 
TO SHOW EFFECT OF VARYING AMOUNTS OF QUARTZ IN POISONED SOLUTION 
No. Length of sprout. Average Remarks 
: 1.5 1.2 I. 0.8 Ae 0.7 1.2 } Roots all dea 4 
2 2.5 25 2.2 1.6 t R I.0 1.8 | Roots all dead ntly 
3 3-1 3.2 3- r.5 2.6 0.7 2.4. | Roots dead and very slig! 
elongat . 
4 2.5 2.2 2.6 2.6 2.5 3.3 2.6 had penetrated into 
liquid but were dead 
5 3-0 5-3 3.0 2.5 2.9 2.86 ts alive, plants struggling 
6 8.8 11.6 10.7 9.2 10.4 1.7 10.4 | Plants healthy 
7 11.7 10.4 1n.2 10.1 9.0 ro. 1o.5 | Plants healthy 
