FUNGI INJUKIOUS TO PINES. 61 



already dead and exposed to the air ; their influence for evil should not 

 be underrated on that account, however, for although they are sapro- 

 phytes living on the wood, their entrance into the trunk and branches 

 means more or less rapid hollowing of the heart-wood (thereby rendering 

 the tree liable to be thrown by winds, etc.) and the gradual production 

 of injurious substances which soak into the sound parts and pave the way 

 for the advance of the destroying mycelium into living organs. Hence, 

 though such fungi are saprophytes, strictly speaking, in their local action, 

 they nevertheless act towards the whole tree taken as a living 

 individual as parasites which may induce dangerous diseases. 



Remedial measures are of course to be directed to the careful 

 tending and covering of wounds, a mode of procedure which has 

 long been carried out on various trees at Kew, and with decided success, 

 I believe. 



I have . already spoken of Hysterium Pinastri as the cause of leaf- 

 casting. Herpotricliia niyra* causes a tiresome disease on Pinus montana, 

 and also on the Spruce and Junipers at high altitudes. Hysteriuiit 

 brachysporum kills the leaves of the Weymouth Pine, and Faiiow and 

 Seymourf give a long list of American forms that will necessitate much 

 careful investigation before we can determine which are truly parasitic 

 and which merely saprophytic. 



There is in Germany a disease of the Scots Pine known by a name 

 which I may translate "Pine-twist." Its prominent symptoms are con- 

 tortions and curved malformations of the tips of the leading shoots, 

 caused by the invasion of a fungus known as Oceania pinitorquwn. 

 The hyphse of this parasite so torture the epidermal region of the young 

 shoots that their growth in length is no longer equal on all sides ; 

 considerable deformity may result from the curvatures of the healthy 

 parts about the dead infested regions, and even the death of the tips 

 occurs in bad seasons i.e., seasons too wet for the Pine, but very 

 agreeable to the fungus. In dry summers, however, the fungus-layers 

 may die off, and the injured spots be occluded. 



But of all the fungus diseases which affect Pines,' none is more 

 interesting, and few more disastrous, than the one induced by a form 

 long known as Peridennium, and of which P. Pini is the best known. 

 This makes its appearance on various Pines as bladder-like bags of spores 

 protruding from the leaves or cortex, and springing from a mycelium 

 which destroys the cell-tissues, and which may kill the upper parts of the 

 tree by ringing its stem or branches. 



As long ago as 1874, Wolff \ showed that the form referred to is 

 merely the secidium stage of a uredinous fungus found on the leaves of 

 certain species of Senecio, and known as Coleosporium. Further 

 investigations partly confirmed and partly contradicted this conclusion, 

 and led to the separation of species of Peridermium which invade 

 the cortex and branches of the Pines (e.y., Pinus sylvestris, P. SJrobus, 

 P. Laricio, P. montana, etc.) from others which infest the leaves of 

 various species of Pinus. 



The results are too lengthy to describe in detail here, but the gist 

 of the matter may be put as follows. 



* R. Hartig, " Allgemeine Forstliche imd Jagd-Zeitung, " January, 1888. 

 t "A Provisional Host-Index of the Fungi of the United States," Part III. 1891 

 pp. 160166. 



J " Hot. Zeitung," 1874. 



