414 



UREDINEAE. 



The aeeidia appear in June as wrinkled yellow sacs 

 emerging from the bark of swellings. They continue to develop 

 in succession for years on the living parts of attacked 

 branches, but according to Hartig they cease to make their 

 appearance on old stems, even when a mycelium is present. 

 This disease is the cause of great damage to pines, especially 

 where planted as pure forest. One case is recorded ^ of a 

 forest near Kohlfurt where 90 per cent, of the trees in an 



old plantation were 



stag-headed ' 



on account of a deficient 



Fig. 24S. — Peridemiium pini. Section through a diseased stem of Pine showing the 

 gradual killing of the cambium by the fiuigus. (v, Tubeuf phot.) 



supply of water in the crown accompanying attacks of this 

 fungus. Until more is known of its life-history, preventive 

 measures cannot be well extended beyond cutting down 

 infected trees. 



The following species of Peridermium have been observed 

 on species of Fimts: 



A. On the needles: 



Peridermium oblongisporium Fuck, (now Coleosporium senecionis) on 

 Pinus sylvestris and P. austriaca (p. 374). 



P. Klebahni, P. Soraueri, P. Stahlii, P. Plowrightii, and P. Fischeri. 

 On Pinus sylvestris ; related to various species of Coleosporium. 



P. piriforme Peck. On Pinus speeiosa in U.S. America. 



P. cerebrum Peek. On Pinus rigida in North America. 



' Marker at Sohlesien. Forstverein, 189.3. 



