482 PROCEEDINGS OF THE ACADEMY OF [May, 



saii-wood and cambium leads to the accumulation of resin, a 

 brownish -yellow material which appears to be fungus gamboge, as 

 indicated by the following test : A solution of ferric -chloride colors 

 fungus gamboge olive-green or blackish-brown, and in the sections 

 of white cedar so treated a decidedly blackish-brown color is 

 obtained. The material in the tracheids is, therefore, named 

 lentatively fungus gamboge. Besides this material, which seems to 

 form the matrix, there are numerous small rouuded grains which 

 plentifully till the medullary ray cells. These granules stain brown 

 when iodine solution is used, green when methyl-green is used, and 

 brown Avhen Bismarck -brown is applied. The substances which 

 then collect in the diseased stems of white cedar through the meta- 

 bolic changes stimulated by the fungus mycelium are tentatively 

 the following: Proteid bodies, in small rounded granules; resin, 

 ■which is confined to the areas of stem undergoing the most rapid 

 histologic changes ; fungus gamboore, which with the other materials 

 referred to fills the medullary ray cells and plugs the tracheids. 

 Besides these, there are amorphous masses of substance in some 

 of the medullary ray cells. These in the natural state are yellowish 

 iu color. When the sections are stained with methyl -green, these 

 masses become green in color. It is impossible to state at this 

 time what these amorphous masses really are. 



With strong iodine solution the walls of the tracheids color a 

 deep brow'nish-yellow, and this reaction is marked in both the longi- 

 tudinal and the transverse sections. 



The Mycelium of Gymnosporangium biseptatum. 



A study of the mycelium yields some interesting results. These 

 results become of importance when a comjiarison of the mycelia of 

 the different species of Gymnosporangium is made with reference to 

 their growth an duration. Farlow'-^ briefly sketches the character 

 of the mycelium in the American species studied by him. " The 

 mycelium does not differ much from that commonly found in the 

 other Uredinere. It is irregular, much branched and cross parti- 

 tions are rather numerous. Unlike, however, the mycelium of 

 some of the Pucciuiie, that of the species of the present genus is 

 limited in extent, and is not found throughout the whole of the 



^*Farlow, The Gymnosporangia or Cedar Apples of the United States, 

 1880, p. 10. 



