. Contributions from the Botanical Laboratory, vol. 12. Botany; Botany. 824 Phytopathology [Vol. 25 1935] Hutchinson: Gall-forming Peridermium 825 Microchemical tests. In connection with the histological study of sec- tions prepared by imbedding, a series of microchemical tests was made on sections freshly cut on the ether-freezing microtome. In most cases the tissues were sectioned a few minutes after they were removed from the tree. Starch, tannin, fats, resin, gums, cellulose, suberm, cutm, lignm, and pectin were identified by means of tests outlined by Eckerson^ or Stevens (34). . a Physio
. Contributions from the Botanical Laboratory, vol. 12. Botany; Botany. 824 Phytopathology [Vol. 25 1935] Hutchinson: Gall-forming Peridermium 825 Microchemical tests. In connection with the histological study of sec- tions prepared by imbedding, a series of microchemical tests was made on sections freshly cut on the ether-freezing microtome. In most cases the tissues were sectioned a few minutes after they were removed from the tree. Starch, tannin, fats, resin, gums, cellulose, suberm, cutm, lignm, and pectin were identified by means of tests outlined by Eckerson^ or Stevens (34). . a Physiological studies. Quantitative chemical analyses have been made of young twigs from both resistant and susceptible trees with regard to tannin, calcium, and potassium content. Analyses of various samples of soil collected at the base of both resistant and susceptible trees have been made with reference to the quantitative determination of calcium and potassium. Juices expressed from the twigs of resistant and susceptible trees by pulverizing the ground twigs with liquid air and subjecting this frozen mass to a pressure of 200 pounds per square inch for 10 minutes have been used for determination of osmotic pressure and hydrogen-ion concentration. An attempt has been made to reproduce in the resistant twigs the patho- logical changes found following infection. Extractives prepared from galls and from germinating spores were introduced into the tissues through small capillary tubes and also by hypodermic injection. Oxalic acid has been used in the same way, several investigators having reported a rela- tionship of this acid to the pathogenicity of fungi (5, 22). FIELD observations OF HOST REACTIONS In their response to infection the inoculated trees have shown many different reactions ranging from highly susceptible to resistant. For the purposes of this discussion, however, 3 principal types of reaction may be distinguished. Type A occurs only in susceptible trees. During the fir
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