184 



Mycologia 



been found that these rusts developed perfectly normally on plants 

 kept in the greenhouse during the summer and placed in cold 

 frames over winter. Very good results have been obtained by 

 fixing extremely thin free-hand sections of material in Flem- 

 ming's weaker fluid. It is necessary to orient the pieces accur- 

 ately in order to avoid cutting oblique microtome sections of the 

 buffer cells and teleutospore buds. Flemming's triple stain was 

 * used, and when the Orange G in concentrated aqueous solution 

 is employed the buffer cells can be seen very distinctly ; whereas 

 if the other colors predominate, the walls of these large empty 

 cells do not show up conspicuously. Sections were cut io/x thick. 



Gymnosporangium macropus 



Cedar apples were obtained from plants growing at Cold 

 Spring Harbor, N. Y., November 30, 191 7. The cedars were 

 potted and some were placed in cold frames, others were kept in 

 the greenhouse and two were planted in the garden. Galls from 

 artificially infected cedars were also studied and R. C. Faulwetter 

 sent me a large collection from Clemson College, S. C, in January. 



Reed and Crabill (1. c.) describe in considerable detail the 

 growth of the galls caused by this rust. They also studied the 

 growth and appearance of the hyphae in their relation to cells and 

 tissues of the host, and followed the development of the sorus 

 from the early stages. My attention has been focused particu- 

 larly on the method of the origin of the teleutospore and it is on 

 this question in the main that I am unable to agree with Reed and 

 Crabill. One or two other points may be noted, however. These 

 authors had some difficulty in staining the mycelium to show 

 cross-walls and nuclei of haustoria distinctly. I find that the 

 septa appear very plainly in my preparations and the haustoria 

 take a very delicate stain showing the single nucleus in each, or 

 two nuclei when two are present. Neither do I find that the cor- 

 tical layer is noticeably thicker over the pits in the galls at points 

 where sori are to appear. Weimer believes that the formation of 

 these pits is due to the inhibition of the growth of certain paren- 

 chyma cells by the fungus present, while at other points the cells 

 continue to multiply so that depressions result. I find that the 



