INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 9 



of root growth in injured seedlings was most commonly observed 

 from 8 to 12 days after the original cessation of growth. Dr. Perley 

 Spaulding has advised the writer that a year prior to the observations 

 here reported he found this resumption of growth by laterals in 

 injured western yellow-pine seedlings in experimental plats at 

 Burlington, Vt. 



It is seldom possible to recognize acid injury immediately after 

 occurrence. Even after death takes place it is not possible to dis- 

 tinguish the deeper rooted injured seedlings from those killed by 

 parasites, as by the time the seedling gives indications of death 

 above ground the roots are too badly decayed to show what caused 

 death. The best way to detect acid injury is to dig up healthy- 

 looking seedlings in different parts of a plat a week or ten days after 

 the first seedlings come up. The roots of the seedlings will be found 

 to have the following characters: 



(1) Acid-injured seedlings (PI. I, figs. 2 and 3). Length, one-fourth to five-eighths 

 of an inch. Color, if brown at all, tip will be as brown as the rest; root firm throughout. 



(2) Healthy seedlings (PL I, fig. 1). Length, 1 to 3 inches. Color, upper part may- 

 be brown, but tip will be white. 



(3) Damped-off seedlings (attacked by parasites). Length, usually same as healthy, 

 but lower part may be entirely decayed, making root appear short. Some part of root 

 examined will always be found soft from decay, while acid-injured roots are firm 

 throughout. 



Note. — Care is needed to distinguish between the short root of an injured seedling 

 and a healthy root which has been broken off short by accident. With a little prac- 

 tice, the difference between a root tip and a broken end can be easily recognized. 



PREVENTION OF INJURY BY LEACHING. 



The first attempt to prevent injury to germinating seedlings from 

 the residue of acid applied at sowing was by leaching. To different 

 plats in a bed which had received 0.188 ounces of acid at sowing 

 three days earlier, 4, 8, 12, and 16 pints of water per square foot, 

 respectively, were applied. The plats were thereafter given sprin- 

 klings equal to 0.3 of an inch of rain often enough to insure germina- 

 tion, which -took place 1 1 days after sowing. The heaviest initial 

 watering, equivalent to 3.2 inches of retained rainfall, prevented 

 most of the injury which occurred on the other plats, but not all. The 

 plat receiving but 4 pints (0.8 inch) suffered heavily, while the 

 amount of injury in the 8 and 12 pint plats was intermediate. In a 

 second test, with an acid treatment of 0.211 ounce at sowing, fol- 

 lowed by germination in eight days, a 6-inch watering was given 

 three days after sowing. The bed was purposely allowed to become 

 quite dry on the day of germination, and later examination showed 

 that a small number of the pines were injured. In a third test, this 

 6-inch watering was used on a bed which had received 0.313 ounce 

 of acid. The bed was allowed to become somewhat dry 10 days 



7i222°— Bull. 169—15 2 



