466 



FUNGI IMPERFECTI. 



stricted tissue will be found extending quite round the twig 

 (Fig. 293). At these places the bark and cambium have been 



killed, whereas the higher 

 portions of the twig have 

 continued to increase in 

 thickness. Numerous 

 small black pycnidia 

 break out on the bark 

 of diseased places and 

 give off small unicellular 

 spindle-shaped conidia, 

 which convey infection 

 to new hosts in August 

 or September. Killed 

 branches die and dry 

 up without casting their 

 needles.^ 



Ph. pithya Sacc. 

 causes a disease similar 

 to the preceding on the 

 Douglas fir {Psendots^iga 

 Douglasii). The pycnidia 

 of the fungus are found 

 on dead constricted parts 

 of twigs, and they, as well 

 as other symptoms of the 

 disease, closely resemble 

 those of Phoma ahietina. 

 Eostrup^ defined and de- 

 scribed it as Ph. pithya 

 Sacc. Magnus also re- 

 cords it on branches of 

 Piniis sylvestris in Berlin 

 botanic garden. 

 Other species of Phoma frequent other conifers and broad- 



FlG. 293. — Phoma alietina. Twig of Silver Fir show- 

 ing ihe constriction characteristic of this disease, 

 dotted over with pycnidia. (After R. Hartig.) 



^Bohm (Zeitsch. f. Forst- u, Jagd-wesen, 1896, p. 154) describes and figures 

 an attack of this parasite on Pseudotstiga Douglasii in North Germany. One 

 cannot, however, avoid suggesting some confusion between this and Ph. pithya 

 described next. (Edit.) 



^E. Rostrup Undersoegelser over Snyltes vampes Angreb paa Skovtraeer, 

 1883-1888. 



