THE ROSE PHRAGMIDIUM 



117 



The Rose Phragmidium 



Phragmidium speciosum 



The peculiar appearance of this disease when attack- 

 ing the stems of roses is well illustrated in Fig. 52 a. 



The bark of such 

 stems is more or less 

 covered with irregu- 

 lar black patches, con- 

 sisting of vast num- 

 bers of the winter 

 spores of the fungus, 

 borne upon long slen- 

 der stalks, as seen, 

 much magnified, at b. 

 The spores themselves 

 are divided by trans- 

 verse partitions into 

 from five to seven 

 cells. The mycelium 

 of this fungus devel- 

 ops in the inner bark 

 and the cambium 

 Mira // // \ layer of the stems, 



but is believed not to 

 penetrate into the 

 woody tissue. Of 

 course it interferes 

 with the flow of sap, 

 and when, as often 

 a happens, it extends 



clear around the stem, 

 it may prove fatal to 

 the plant. The mycelium is perennial in the stems, 

 living from one season till the next, so that when once 

 infested there is no way of ridding a plant of it. The 



b 



FIG. 52. ROSE PHRAGMIDIUM. 



a. Affected stem; 6, winter spores. 



