INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 15 



place at this time. It was most serious in the 0.375-ounce plat, 

 mainly because it had become somewhat drier than the rest. Even 

 the 0.281-ounce plat seemed more injured than the 0.687-ounce 

 plats, which were not seriously affected. The activity of parasites, 

 mostly, probably, Pythium debaryanum, in the soil in these plats 

 during and after the time that this injury was occurring to the 

 seedlings is a matter of some interest. The slight relationship 

 between the amount of acid used and the amount of injury taking 

 place in these plats 22 days after treatment emphasizes what has 

 already been said as to the apparent equalization of strength of 

 acid solutions of different original strengths in the soil as the con- 

 centration decreases. 



Plats of jack pine which had been entirely killed by applications 

 of 0.172 ounce of acid at the date of germination and 0.086 ounce 

 six days later, 0.258 ounce in all, were resowrj, with the same species 

 23 to 24 days after the first treatment, germination taking place 

 34 to 36 days after the first treatment. No serious injury occurred 

 to the seedlings in this second sowing, though no special watering 

 was given. Similar results were obtained with yellow pine in plats 

 treated with 0.3 ounce of acid 39 days before sowing (50 days before 

 germination), no serious injury occurring despite the entire lack of 

 any special watering. In all cases, acid applied before sowing can 

 be kept from causing injury quits easily by the watering methods 

 used for beds treated at sowing. The tests indicate that if germina- 

 tion takes place at any time during the first month after 0.25 ounce 

 of acid is applied to the beds it will be necessary to give more than 

 the usual nursery watering during the germination period in order 

 to insure freedom from injury to the seedlings. Though it is some- 

 what easier to prevent acid injury in beds treated several days 

 before sowing, treatment at the time of sowing is so much more 

 effective against the damping-off parasites that it is considered 

 preferable. 



RELATIVE RESISTANCE OF VARIOUS SPECIES OF PINE TO SULPHURIC ACEO. 



There was .considerable difference in the amount of injury caused 

 by similar acid treatments on different species of pine. Jack pine, 

 as a rule, seemed most liable to serious injury, while yellow pine was 

 least often damaged, and Norway and Corsican pines were intermedi- 

 ate. The resistance of yellow pine as compared with jack pine was 

 especially evident in beds treated shortly after germination. Most 

 of this apparent difference in resistance is due not to variations in 

 the capacity of the root tips to endure acid, but to a difference in 

 the rate of growth. Yellow pine has a seed approximately ten 

 times as heavy as that of jack pine and sends its root down much 



