. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. 40 Phytopathology [Vol. 28 Table 1 shows some divergences between the ash of the galls and the rust- free wood. The greater amounts of nitrogen, sulphur and phosphorus in the galls can perhaps be correlated with the large quantities of food sub- stances stored in them. The lesser amounts of silicon present in the galls appear to add a chemical reason to the structural basis of the mechanical weakness shown by gall wood. Most of the results, however, show difference
. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. 40 Phytopathology [Vol. 28 Table 1 shows some divergences between the ash of the galls and the rust- free wood. The greater amounts of nitrogen, sulphur and phosphorus in the galls can perhaps be correlated with the large quantities of food sub- stances stored in them. The lesser amounts of silicon present in the galls appear to add a chemical reason to the structural basis of the mechanical weakness shown by gall wood. Most of the results, however, show differences whose explanation is at present difficult. Perhaps when the complexities of the physiology of the host-parasite relationship are better understood these figures may appear more significant but here the methods of ash analysis appear to shed little light on the physiological aspects of the problem. R]gsUME OF THE LIFE CYCLE AND MORPHOLOGY OF THE WOODGATE PERIDERMIUM The Woodgate Peridermium is autoecious and has but 2 known spore forms, pycnia and aeciospores. The pycnia were first found during the course of this study. They were discovered in material collected on May 17, which had been selected to show developmental stages of the gall and in choosing and fixing the material, the pycnia had been passed over unnoted. Later, other inconspicuous internal pycnia were found in sections of material from several young galls collected in the same season some of which had shown external traces of exudate at the time of collection. The aeciospores reinfect the host directly. They are roundly and irregularly rhomboid with verrucose walls. No germ pores have been observed in the walls of the aecio- spores. (Fig. 3, D). They may germinate on water or upon the host in from 12 to 24 hours. The germ tube protrudes often but not always from an apex of the spore and broadens to form a septate branching hypha, which within the inoculation chamber, may apparently penetrate the host at once or gr
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