AGRICL ,-* 



LIBRARY 



OBSERVATIONS ON RHIZINA INFLATA 



By JAMES R. WEIR, 



Forest Pathologist, Investigations in Forest Pathology, 

 Bureau of Plant Industry 



Considerable doubt exists regarding the parasitism of Rhizina inflata 

 (Schaff.) Sacc. (R. undulata Fr.). This peculiar fungus (PL VIII, figs. 

 1,2, and 3) occurs quite abundantly on the ground in the forest-fire areas 

 of the Northwest. Usually found as a saprophyte on the burned forest 

 soil, it attracted little attention until the close proximity of the fruiting 

 bodies to dead coniferous seedlings was noted to be of frequent occur- 

 rence. A close examination of the roots of the dead seedlings showed 

 the mass of white mycelium clinging to and ramifying in the cortical 

 tissues of the root to be in connection with the near-by fruiting structures 

 of Rhizina inflata. In some cases the sporophores of this fungus sur- 

 rounded the stem of the seedling. 



The observations on the parasitism of this fungus are not extensive. 

 The disease "la maladie du rond" of Pinus sylvestris and P. maritima, 

 according to the investigations of Prillieux and De la Boulaye (iSSo), 1 

 is accredited to this fungus. Hartig (1891, 1892, 1894, p. 123-129) 

 afterwards in more thorough investigations substantiated the observa- 

 tions of the former investigators and showed Rhizina inflata to be capable 

 of living as a true parasite, causing the death of 4- year-old seedlings of 

 Abies pectinata, Pinus strobus, Larioc europaea, Picea sitkaensis, Tsuga 

 mertensiana, Pseudotsuga douglasii, and Castanea vesca. Von Tubeuf ( 1 897 , 

 p. 273) also reports the fungus as a parasite in the forest-tree nurseries 

 of Germany and in the natural forests of Pinus pinaster in France. 



Early in the spring of 1912 at a certain point along an old logging road 

 in the Kaniksu National Forest, Idaho, where the brush had been burned, 

 young 3- to 5-year-old seedlings of Tsuga heterophylla, Larioc occidentalis, 

 and Pinus monticola were observed to be dying in small isolated patches. 

 The roots of the seedlings on being pulled up were closely matted together 

 by a white mycelium, causing a quantity of earth to adhere to them. 

 Since fungous fruiting bodies were not in evidence on any part of the 

 diseased plants or on the ground around, the death of the seedlings was 

 attributed to Armillaria mellea (Vahl) Quel., which is very abundant in 

 this region and is frequently the cause of the death of very young growth. 

 The mycelium had penetrated all parts of the cortical and bast tissues of 

 che roots, causing them to become saturated with resin, a condition 

 quite similar to that produced by A. mellea. The diseased areas were 



1 Citations to literature in parentheses refer to " Literature cited," p. 95. 



Journal of Agricultural Research, Vol. IV, No. i 



Dept. of Agriculture, Washington, D. C. Apr. 15, 1915 



G-44 

 (93) 



