BLIGHTS OF CONIFEROUS NURSERY STOCK. 7 



ease to water loss, may be mentioned. Losses have frequently been 

 more serious in the nursery transplant beds than in the trees planted 

 out in the sand hills, where there is little humus and no wind pro- 

 tection and where no artificial watering is done. This was advanced 

 as an argument against drought as a cause of the trouble. The fal- 

 lacies in this argument are that the trees used in the hills had been 

 previously once transplanted, so that they were stronger and better 

 rooted stock, and that in the hill plantations there was not so much 

 competition as in the transplant beds, where the close stands of trees 

 exhaust soil moisture very rapidly. 



Another argument against drought as a cause of the disease was the 

 fact that in certain cases the blight appeared at Halsey when the soil 

 2 or 3 inches down seemed quite moist. However, further examina- 

 tion and quantitative determinations of moisture content showed that 

 at such times the soil around the mass of absorbing roots is drier 

 than the soil near the surface. The dense stands of seedlings appar- 

 ently exhaust the soil moisture at the lower levels more rapidly than 

 evaporation takes the water nearer the surface. 



A further argument advanced against the drought theory is the 

 fact that at Halsey trouble often occurs within a very few days after 

 fairly heavy rains. This happens, however, only in very drying 

 weather and in beds where the stand is dense. Under such conditions 

 the moisture is drawn from the sandy soil very rapidly, so that in all 

 such cases the soil around the roots is found to be very dry despite 

 relatively recent rains. 



One case of sun scorch occurred at Halsey in 1910 which was quite 

 difficult to explain, although the evidence presented by adjacent plats, 

 some of which had been shaded and some especially watered, left 

 little doubt as to its relation to drought. On July 25 and 26 a period 

 of hot weather culminated in temperatures of 100° and 96° F., respec- 

 tively. At about 7 a. in. July 27, 0.28 inch of rain fell. The sky 

 cleared immediately after, the temperature rose to 102°, and the air 

 became dry. July 28 was cool and cloudy. On that morning a large 

 number of the smallest grade of 2-year-old jack-pine transplants had 

 begun to turn yellow, and in 24 hours about one-third of all the 

 stock of this class showed injury. Trees continued to turn yellow 

 and die in decreasing numbers during three or four days of cool, 

 partly cloudy weather following till the loss reached fully 50 per 

 cent. The 0.28 inch rain of the 27th appeared to penetrate to the 

 roots through the rather coarse soil. The best explanation seems to 

 be that the roots were injured by the excessive demand on them dur- 

 ing July 25 and 26, before the rain fell, or on July 27, before the rain 

 had time to get down to the root level. The failure of the tops to 

 show injury till some time after the roots are hurt is always more 

 marked in transplants than in seedlings. There seems to be no rea- 



