48 ELEVENTH REPORT. 



NOTES ON PLANT PATHOLOGY. 



James B. Pollock. I 



GANODERMA SESSILE MURRILL A WOUND PARASITE ON MAPLE. 



In 1905 the writer reported at a meeting of the Michigan Academy of Science 

 an observation that suggested the possible i^arasitism of Ganoderma sessile 

 Miirrill (7th Report Mich. Academy Science). The fungus and the maple 

 tree there mentioned have been kept under observation until the present 

 time, and the results confirm the view there expressed that the fungus is at 

 least a wound parasite. In the seasons of 1905 and 1906 the fungus fruited 

 anew at the base of the tree, hardly rising above the level of the ground, 

 .■<een first on June 4th. The gro\\i:.h is at first nearly pure white, turning 

 yellow and finally red in a somewhat irregular way. In 1905 it extended 

 a little more than half way around the trunk, not in an uninterrupted sheet, 

 but in four different patches. In 1908 it ceased to fruit except in one of 

 these patches, and on the side where the sporophores had occurred for the 

 several preceding 3^ears (under observation since 1904) the wood of the trunk 

 is completely decayed in to the center of the tree. Between this decayed 

 portion and the spot where the sporophore occurred in 1908 there is a strip 

 of cam))ium still alive, but where this last sporophore developed is another 

 area of dead cambium. 



Since in the last three years the fungus has made hardly any progress 

 around the trunk of the tree, it shows little if any ability to attack the live 

 camljium, but it possesses the ability to attack and completely destroy the 

 exposed wood both sap and heart-w^ood. Ganoderma sessile is therefore 

 to be placed among the wound parasites, at least for the sugar maple, Acer 

 saccharum Marsh. The primary injury to the tree which enabled the fungus 

 to get its start, was probably "the cutting off of roots in building concrete 

 walks near the tree. Every year the difference in size between this tree and 

 the others in the same roAv is becoming more marked. !J if S ^ I 



POLYSTICTUS HIRSUTUS FR., A WOUND PARASITE ON MOUNTAIN ASH. 



For several years two mountain ash trees were observed each of which had 

 one of its main branches partly dead, and in each ease the dead parts were 

 partly covered by sporophores of Polystictus hirsutus Fr. In both cases 

 the diseased condition was progressive for several succeeding years, the trees 

 gradually dying off. When one of these trees was dug up it was found to be 

 badly rotted at the heart throughout the trunk. In this rotten heart wood 

 was "found the mycelium of the same fungus whose sporophores were found 

 on the outside of the dead branches. On pieces of the rotten heart wood 

 placed in damp chambers sporophores of the fungus developed in about two 

 months. 



THE CONIDIAL FORM OF A SCLEROTINIA ON PRUNUS SEROTINA. 



On May 30, 1905, the writer observed in the vicinity of Ann Arbor, Mich, 

 a number of wild black cherry trees {Primus serotina) which even at a con- 



