SOIL TREATMENTS AND SEED GERMINATION 33 



and that is the quantity which, in the work of Beach (8), protected lettuce against 

 Sclerotinia although plants were injured chemically. A dilution of 1:1600 had 

 some effect in protecting violets against Rhizoctonia (72), and as little as 0.12 gm. 

 (per square foot) was effective, in the experiments of Wiant (97), in protecting 

 conifers against Rhizoctonia. Stands of tomato were injured by 0.44 gm., not by 

 0.22 gm., as used by Thomas (85); and as light an application as 10 to 15 pounds 

 per acre (about 0.10 to 0.15 gm. per square foot) was observed by Macleod and 

 Howatt (60) to be associated with reduced yields of potatoes. 



The writer applied mercuric chloride, 1 or 2 quarts of the solution per square 

 foot, to soils which had been inoculated or were naturally infested with both 

 Pythium and Rhizoctonia. There was sometimes some damping-off with 0.95 

 gm., equal to 2 quarts of a 1:1000 solution, or 1 quart of a 1:2000 solution per 

 square foot. There was little or no damping-ofT with applications heavier than 

 1.0 gm. per square foot, but such applications were very harmful to germination 

 or growth of some of the species named in Table 14, although a number of species, 

 notably Salpiglossis, Petunia, lupine, sweet pea, and English daisy, finally out- 

 grew most of the earlier chemical injury. 



Table 14. — Effect of Mercuric Chloride on Germination and Growth 



Germination Growth 



Species Not Not 



injured Injured injured Injured 



by by by by 



Gm. Gm. Gm. Gm. 



Arabis 1.5 1.5 



Canterbury bells 1.0 - — 1.0 



Dianthus chinensis and\ 



D. plumarius j 2.5 1.5 2.0 



English daisy ' 3.0 - — 1.0 1.5 



Foxglove 1 . 5 — - 1 . 5 



Heliotrope 1.5 - — 1.5 



Lupine 2.5* 1.75 2.2 



Pansy 1.5 2 1.0 



Petunia 1.7* 2.5 1.5 2.5 



Salpiglossis 2.0* 2.2 2.7 



Sweet pea 2.5* 3.0 2.0 2.2 



Rhododendron niolle and 1 



R. yedoense var. poukhanensej - — ■ 1.5 



Beet 2.5 3.0 2.0 



Cucumber 1.7 2.0 1.5 



*Germination improved. 



The species least injured as regards growth and most benefited as regards 

 germination were Salpiglossis, Petunia, lupine, and sweet pea, and with these the 

 use of mercuric chloride as a soil fungicide appears to deserve further investiga- 

 tion. 



