CURRENT LITERATURE. 269
species of conifers in various localities, but particularly in swampy places or under conditions of extreme humidity. Heavy irrigation was found to induce such lenticels as was also the pruning of the shoots.
The literature on hypertrophied lenticels is briefly reviewed. Schenk attributes the phenomenon to oxygen hunger. Later writers think, it to be caused by humidity, moist air allowing the continued formation of aerenchyma while dry air induces suberization and cork formation. De Vaux thinks humidity increases lenticellular development entirely through increase of sap pressure. Soraurer connects them with general pathological conditions of the tree. The authors are inclined to go back to the older theory that oxygen huDgeriS the main predisposing cause. They feel, however, that other factors contribute to the result, and suggest that the problem can be best attacked by experiments in which oxygen, carbon dioxide and water supplies in the soil are independently controlled.
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