ANNUAL REPORT, 1942 19 



steaming, by formaldehyde, or by vinegrr within 24 hours before the insertion of 

 winter cuttings, there was injury to arbor-vitae, red cedar, Hinoki cypress, yew, 

 and two species of Ilex. Similar treatment of the rooting medium with steam or 

 formaldehyde four days before the insertion of cuttings was also harmful or of no 

 benefit. Such treatments are apparently more tox'c to cuttings, even dormant 

 cuttings, than to some seeds and it is evident that there should be considerable 

 delay between the disinfection of a rooting medium and the planting of cuttings. 

 Cuttings of white pme, made of the previous year's growth, were taken in late 

 wnter. They rooted neither more nor less well in sand-peat previously used for 

 this purpose, or in sand-peat to which soil from under pine trees had been added, 

 than they did in new sand-peat, never before used, or in new sand-peat steam- 

 sterilized fifteen days previously. Fungi in the rooting medium are, it appears 

 from this, without effect on the rooting of cuttings of white pine. Cuttings from 

 difi^erent white pine trees differ in rooting capacity, and treatments which improve 

 the rooting of cuttings from some trees are without much or any effect on the 

 rooting cf cuttings from others. Rooting of cuttings from some trees was im- 

 proved by relatively short solution-immersion treatments in relatively concen- 

 trated indolebutyric acid or napthaleneacetic acid solutions, by powder-dip 

 treatments with Hormodins No. 2 and No. 3, and by combinations of solution- 

 immersion and powder-dip treatments. 



Effect of Chromated Zinc Chloride on Plants. (L. H. Jones.) The scarcity of 

 lumber which is naturally decay-resistant has led to the use of a chemically treated 

 substitute. This has been successful in the case of telephone poles, railroad ties, 

 building supports, etc. However, when such chemically treated lumber was used 

 in the construction of benches in which plants are grown in the greenhouse, re- 

 sults have indicated that the wood preservative may be toxic to the plants, in- 

 stead of only to the fungi and bacteria which cause decay. 



In tests made here, where chromated zinc chloride was used as the preservative, 

 injury to growing plants was very common and was most pronounced during the 

 warmer months and with the more acid soils. 



Study of Diseases of Plants Caused by Soil-Infesting Organisms, with Par- 

 ticular Attention to Control Measures. (W. L. Doran.) Seed treatment with a 

 mixture of oxyquinoline sulfate and talc (1:1) markedly improved stands, but 

 seed treatment with a mixture of potassium dichromate and graphite (1:1) gave 

 even better results; as good results, in fact, as did Semesan, Spergon, or red copper 

 oxide with cucumber, cress, beet, tomato, and chicory. Only with pea did Sper- 

 gon give better results than potassium dichromate. With tobacco, red copper 

 oxide as a seed treatment gave the best results, Spergon the poorest; but none 

 of the seed treatments gave as good results as did formaldehyde treatment of soil. 



Sodium nitrite, 1.5 to 3.0 gm. per square foot, applied to soil immediately after 

 seeding, was injurious to crucifers and to pea, not to cucumber, beet, and chard, 

 and it markedly increased the number of plants which lived. Lacking anything 

 better, it could be used as a soil fungicide with some plants, but it did not give 

 so good results as did much lighter applications of potassium dichromate. 



Chromates and dichromates of potassium, ammonium, and sodium, applied 

 in solution to soil immediately after seeding, were found to be highly effective soil 

 fungicides, as effective as formaldehyde even in light applications. And, if prop- 

 erly used, they were quite safe as regards effects on germination and growth of 

 seedlings, except with cabbage and other crucifers. Potassium dichromate, 0.4 

 or 0.45 gm. per square foot (about 43 pounds per acre), was usually enough for 

 protection and great improvement in the stands of seedlings whether the pH value 

 of the soil was 5.6 or 7.1; but the treatment was safer and less likely to retard 



