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A study of the species of the form genus Periderwium occurring on the needles of pines in the United States, and of their relation to the various species of Coleosporium in the same range was begun by the senior writer in 1912. He has since been assisted in this work as follows: by William H. Long in 1914, by N. Rex Hunt from 1915 to I918, and by Glenn G. Hahn in I919 and I920. All collections cited in this paper without the name of the collector were made by the senior writer; where made by others the name of the collector is given. This paper gives some of the results of the more critical sets of inoculations made with

The black poplar (Populus nigra L.), especially the variety known as the Lombardy poplar, is one of our most beautiful ornamental trees. It is, however, subject to diseases which shorten its life. In the United States these diseases apparently have not been studied to any extent, as there is a lack of literature on the subject. During the spring of I916, many reports were received by the United States Department of Agriculture concerning a serious blight of newly transplanted black poplars. In one instance, every tree in a lot of thirty was killed back by cankers. In a second instance, nearly all of 630 trees were badly infected with cankers, and at least one fourth of them were killed back to the point of the infection. An examination of cankers from the trees mentioned above