420 



DISEASES OF CULTIVATED PLANTS 



Phlox stem canker. The stems of various cultivated kinds 

 of Phlox are sometimes attacked just above the ground- 

 line by Pyrenochaeta phloxidis (Massee), the result being a 







Fig. 131. 1 x. Pyrenochaeta phloxidis, section of phlox stem 

 showing two perithecia, mag. ; 2x, spores of same, mag. ; 1 x\. 

 Phi icanthi, on hawthorn leaf ; 2 xx, section of spore- 



bed of same, mag. ; 3 xx. spores of same, highly mag. ; 1 xxx, 

 Coniothyrium hellebori, on leaf of black hellebore ; 2 xxx, spores 

 of same, highly mag. 



cankered appearance, which results in the death of the stem 

 attacked. The leaves turn yellow and drop off, followed by 

 the breaking of the stem near the base. The minute, black, 



