INJURY BY DISINFECTANTS TO SEEDS AND EOOTS. 17 
siderable quantities for the first two or three weeks, after which time 
the number which came up decreased. 
Most of the data on the effects of sulphuric-acid treatments on 
weeds were obtained on beds treated at the time of sowing. The 
observations indicated marked differences between the species 
observed in their ability to grow in soil recently treated with acid. 
It was evident throughout that the pines were less easily injured than 
most of the weed species. On plats which received no special water- 
ing till after germination, 0.125 ounce and 0.141 ounce of sulphuric 
acid per square foot, respectively, at the time of seeding entirely 
prevented weed growth. The untreated plats in this series were 
fairly well covered with Portulaca aud grass species and with a few 
plants of Amaranthus. At sowing in another series on a plat given 
very frequent watering, 0.125 ounce of acid failed to reduce per- 
ceptibly the number of common weeds. Another plat given the same 
treatment, which had also received 0.125 ounce of acid 13 days before 
sowing, showed entire freedom from weeds, with only partial injury 
to the pines. In repeated tests during successive seasons, treatments 
of 0.188 ounce of acid at the time of sowing regularly prevented 
practically all weed growth for the first three weeks after the germi- 
nation of the pines. In some cas§s no weeds came up in treated beds 
until a month after the appearance of the pines. Beds treated with 
acid and so watered as entirely to prevent injury to the pines were 
nevertheless so free from weeds as a result of acid application that 
the cost of weeding the treated beds during the whole season has 
been only one- third that of untreated beds. 
The appearance of Equisetum in acid-treated plats was of some 
interest. In an insufficiently watered acid plat on which the pines 
were seriously injured and on which not a single phanerogamic weed 
appeared, more Equisetum developed than in most of the untreated 
beds in the nursery. Equisetum was not a common weed anywhere, 
but it occurred more frequently in the acid beds than in the beds not 
treated. 
The grasses throughout gave evidence of greater ability to endure 
the acid applied to the soil than did the dicotyledons. They were 
usually the predominant weeds and often the only ones in acid plats. 
This greater predominance of grasses over dicotyledons in the acid 
plats left little doubt as to their superior endurance of this treatment. 
Unfortunately, few data were secured as to the factors which con- 
trolled the varying capacity of the different plants observed to 
endure acid applied to the soil. Most of the injury to the weeds did 
not occur in just the same way as to the pines. In the pines the 
commonest phenomenon was root injury, which allowed the seedlings 
71222°— Bull. 169—15 3 
