ANNUAL REPORT, 1944-45 23 



Changing the soil temperatures from the low to high and from the high to low- 

 altered the shape of the new leaves formed after the change of temperatures. 

 Those plants which had been growing at the low of 70°F. with normal leaves 

 soon produced frenched leaves at the tip when the soil temperature was raised 

 to 90°F. On the other hand those plants which had been growing at 90°F. soil 

 temperature and had produced frenched leaves at the tip reacted to the dropping 

 of the soil temperature to 70°F. by sending out lateral shoots, the lower leaves of 

 which were frenched but as the shoot grew the leaves developed with less french- 

 ing and were practically normal at the tip. 



Toxic Effect on Plants by Wood Preservatives. (L. H. Jones.) Continuation 

 of the work previously reported on creosote injury to plants showed that the 

 injury was local. The fumes are evolved from creosote-treated lumber by the 

 high temperature of the sun's rays and pass into the leaves of plants through the 

 stomata. An exposed leaf on a vine or stem may be killed, but the creosote fumes 

 are not transmitted by the vascular system to adjacent parts. However, if the 

 injury is in the region of the growing point, further growth is stopped and the 

 plant will die unless the nature of the plant allows the development of lateral 

 shoots, one of which may become a leader. 



No injury resulted from attempts to have creosote or its fumes absorbed through 

 roots of plants in the soil. Seedlings of cabbage protected from creosote fumes 

 by glass shells were uninjured although the creosote fumes were free to enter the 

 soil and be absorbed by roots. One teaspoonful of creosote mixed with the vol- 

 ume of soil in a 3-inch pot failed to give injury even with a recorded soil tempera- 

 ture of 108°F. Creosoted tomato stakes with the creosote slightly above the 

 soil line did no harm to plants, when young or at any time during the season. 



Cabbage maggot protectors made of heavy paper impregnated with creosote 

 did not injure cruciferous plants except when the stalks were soft and tender. 

 Unhardened plants were liable to be burned by the fumes where the impregnated 

 paper came in contact with the stalk. Injury also occurred when growers failed 

 to remove translucent hoods before the sun's rays became strong enough to 

 volatilize the gases of creosote in the paper, which were then confined under the 

 hoods. Tests made with these protectors tacked to lath and placed close to 

 radish rows resulted in injur}' to the radish plants. Even after the radish plant 

 had four true leaves and was four inches high, injury resulted and the leaves were 

 severely injured. Probably the closeness of the leaves did not allow good air 

 drainage and the fumes collected about the leaves. 



Lumber with the trade name of Asidbar, impregnated with resins from which 

 the more volatile constituents had been removed, was injurious to seedlings of 

 cabbage and tomato when the lumber was at a higher level than the seedlings. 

 The injury was similar to creosote injury, resulting in a rolling upward and in- 

 ward of the margins of the cotyledons and first leaves of cabbage and tomato. 

 Death of the seedlings was frequent. Injury did not appear during cloudy 

 weather but followed hot sunny da^'s, indicating that some fumes are evolved by 

 the influence of the sun's rays. Asidbar lumber buried in the soil in close prox- 

 imity to seeds of tomato and cabbage gave no indication of a toxic effect. In 

 fact the roots of the seedlings developed in contact with the wood, remained white 

 and developed branches in contact with the wood. A recorded soil temperature 

 of 96°F. on a hot day was not followed by any indication of injury from this 

 lumber protected from the sun's rays by the soil covering. 



Cuprinol, a copper naphthenate, when used as a wood-preservative paint did 

 not injure plants. Before plants or seeds were used near the painted wood, a 

 week was allowed to elapse in order that the volatile carriers of the preservative 

 might evaporate. 



