INJURY BY DISINFECTANTS TO SEEDS AND HOOTS. 



The procedure followed in treatment at sowing time was to (1) 

 prepare the seed bed, (2) soak it with the disinfectant, (3) sow the 

 seed broadcast, (4) cover with one-fourth inch of dry soil, and (5) 

 apply the rest of the solution. The seed bed was not stirred up after 

 the application of the solution was commenced. In no case in 

 spring-sown beds has there been any indication that the treatments 

 injured the pine seed before germination started, although the treat- 

 ment, in strengths varying from 0.125 to 0.375 fluid ounce of acid 

 per square foot, has been tested during the past three seasons in 19 

 different experimental series of jack pine, in 4 series each of yellow 

 pine and Norway pine, and 1 series of Corsican pine. The proportion 

 of germination in acid plats was nearly always higher than in the 

 untreated plats (due to the prevention of parasites rather than to 

 stimulation), and as high as in plats of soil disinfected by heat. 



In jack-pine plats in which germination was reasonably prompt 

 (12 to 14 days) and no special measures were taken to prevent injury 

 to seedlings, many seedlings were killed or injured after germination 

 began on plats which had received, respectively, 0.125 ounce and 

 0.141 ounce of acid per square foot at sowing, while 0.188 ounce per 

 square foot always resulted in injury unless special protective 

 measures were taken. 



DESCRIPTION OF THE INJURY. 



Injury to the seedlings in plats treated at or before the time of 

 sowing took the form of damage to the growing apices of the radicles, 

 with the result that extension of the root was stopped. 

 Whether the meristematic apical cells were actually 

 killed or simply lost their meristem qualities was not 

 determined, though the former is the more probable. 

 In most cases, root apices rendered incapable of growth 

 retained their normal cream color for a few days after 

 the injury and often recovered, though in severe cases 

 they turned dark very soon. Plate I and text figures 

 1 and 2 show chemically injured seedlings. Plate I, 

 figure 1, shows a healthy seedling, younger than the 

 injured seedlings in figures 2, 3, and 4 of this plate, so 

 that the darker color of the upper parts of the roots of 

 injured seedlings is chiefly due to difference in age, 

 rather than to the effects of the acid. The dispropor- 

 tionately short roots of the injured seedlings are espe- 

 cially noteworthy. 



Ordinarily the growth of cells just back of the apex 

 was not entirely prevented, so that the root tips be- 

 came truncated as a result of the uneven growth. 

 (PI. I, fig. 2.) Distorted growth was also common. The capacity 

 for absorption was usually retained by the injured roots for some 



Fig. 1. — Pinus di- 

 varicata injured 

 by acid. Root 

 growth has just 

 been resumed by 

 two laterals after 

 11 days suspen- 

 sion. X 1J. 



