30 MASS. EXPERIMENT STATION BULLETIN 351 



and Petunia, Nicotiana and Primula polyantha were not much less sensitive. 

 It is not likely that aluminum sulfate can be used safely for the protection of such 

 species. Calendula and sweet pea were less injured, and most tolerant of all were 

 the species of Dianthus, for they were not injured by 44 gm. and their early growth 

 was, in fact, improved by 20 gm. 



Table 13. — Effect of Aluminum Sulfate on Growth of 

 Different Species 



Species 



Calendula 



China aster 



Dianthus sps.* 



Foxglove 



Laburnum 



Lupine 



Nicotiana 



Petunia 



Primula polyantha 



Snapdragon 



Sweet pea 



Beet • 



Cucumber 



*Ali the species of Dianthus which are named in the appendix. 



Copper and Copper Salts 



The copper salts here mentioned were very thoroughly mixed with soil which 

 had been inoculated with Pythium, for, as was shown by Hunt and his co-workers 

 (50), their penetration in and through soil is poor. No use was made of Rhizoc- 

 tonia, against which several investigators (70, 85, 79, 38, 97, 89) have found 

 copper salts rather ineffective. Especial attention was paid to their effects on 

 germination and on growth of seedlings, for the literature suggests that copper 

 in soil-fungicidal quantities may be far from safe to some species. 



Metallic Copper Powder^ 

 This metallic copper, manufactured electrolytically in crystalline form, gave 

 some degree of control of damping-off when not less than 10 gm. was applied to 

 soil before seeding; but the growth of several species (mignonette, foxglove, 

 sweet alyssum, Viola cornula, snapdragon, heliotrope, Pentstemon ovatus, China 

 aster, sweet pea, and Calendula) was injured by it. 



Cuprous Cyanide 

 There was little or no damping-off with 2 gm. cuprous cyanide; but no 

 salt of copper used was any more toxic to plants, especially to Ageratum, Petunia, 

 Salpiglossis, beet, and cucumber, and 2 gm. injured germination of beet and 

 cucumber more than did 3.5 gm. copper carbonate. Hollyhock was the only 

 species satisfactorily protected by cuprous cyanide without some chemical injury. 



'Copper powder, "B" metal from United States Metals Refining Company. 



