448 PROTECTION A(;AINST FUNGI. 



i. AnioK OF Animals. 



Biting l)y cattle, chiefly goats, or l)y deer, mice, mites, or 

 insects. The witches-broom on lihac, for instance, is caused 

 by mites {Phytopus Loeici, Nal.) ; also on willows {Phiitopus 

 triradiatus, Nal.), etc. 



ii. Action of Plants. 

 Parasitic fungi cause witches-broom on silver-fir {McJamp- 

 sorclla Caryophyllacearum, Schroter), No. 8. On li(jrnbeam 

 {Exascus Carpini, Rostr.) ; Birch {E. be tuUn us, Kostv.) ; cherry 

 (E. Cerasi, Fuckl.), etc. It is not known what causes witches- 

 broom on Scots and Weymouth pines, spruce, larch, or beech. 

 Hoffmann, of Giessen, states that two species of Cladosporium 

 cause this hypertrophy on Scots pine, but this is still unproved. 

 Goeppert states that it is due to a local swelling of the 

 cambium, but does not explain how this arises. These witches- 

 brooms, as well as those on the Scots pine, do not appear to 

 be very prejudicial to their hosts : that on silver-fir is described 

 under next heading. 



*8. MehiwpsorcUa Caryophyllacearum, Schroter, formerly 

 named .Eeidiuni elatinum. Link.* 

 (Silver-fir Canker.) 

 a. Description and Life-history. 



This fungus causes the well-known silver-fir canker and 

 witches-broom. The latter may be distinguished from normal 

 shoots of silver-fir by its erect, brush-like growth, resembling 

 the parasitic growth of mistletoe, on the drooping branches of 

 the fir, and by the small yellowish-green needles growing all 

 round the shoot, which fall off in their first autumn. There 

 is also a slight swelling of tlie affected shoot, and in it the 

 mycelium of the fungus grows in the cortex and bast of the 

 host, passing into the younger shoots and needles till the 

 witches-broom, which appears to live only for sixteen years, dies; 

 the mycelium still lives in the cortex of the cankerous swelling, 

 but apparently not in the wood. It does not grow down 



* •' Der Weisstamienkrebs," Dr. Karl N. Heck. Berlin, Springer, lSi)4. Also 

 two papers by E. Fischer in Zeitschrift fur Pflangenkraukheiten, Vol. XI., pt. 6, 

 I'.toi and 19(12, pp. 321—348. 



