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JOURNAL OP THEl ROYAL HORTICULTURAL SOCIETY. 



are dealing with, much may be done by careful pruning and 

 paring, combined with drainage and protection ; but unquestion- 

 ably this Larch-disease is a difficult matter to struggle with 

 when once it has made headway. The best " cure " is, of course, 

 prevention — ^.e., plant sound trees, learn to recognise the earliest 

 stages of the disease, and if it appears cut out the young patches 

 and burn every trace of diseased cortex. 



Very few Larches are cultivated, and I do not know whether 

 the Himalayan L. Griffithii suffers from the disease just dealt 

 with. Farlow mentions Trametes Pini as occurring on L, 

 americana. 



A subterranean fungus known as Bhizina undulata has lately 

 been found to be very destructive to young Larches, Silver Firs, 

 and other Conifers {e.g., Tsuga Mertensiana, Pseudotsuga 

 Douglasii, Picea sithensis, and Pinus Strohus). It seems to 

 belong or be related to an obscure group of fungi known as 

 Uhizoctonia, which still need careful investigation.* 



It will probably be observed that I have followed no very 

 strict classification of the Conifers in this address, but have 

 simply chosen groups convenient for the purpose in hand. I 

 propose to take the remainder of the Conifers in equally arbitrary 

 groups, and first of all certain of the Cupressineae. 



IV. The Junipebs. 



The most remarkable diseases of the Junipers are those due 

 to various species of a uredinous fungus known as Gymno- 

 sporangium, the hyphae of which so irritate the cambial region of 

 the stems of these Conifers (in which the mycelium is perennial) 

 that peculiar woody swellings are produced, sometimes in such 

 quantities as to distort, and even kill, the stems. From these 

 swollen parts of the branches the Teleuto-spores are produced in 

 enormous quantities during the spring, and some most remark- 

 able facts have been elucidated by the researches of recent years — • 

 facts which show that there is still much to be done before we 

 have exhausted the biology of these disease-inducing fungi. 



It has long been known that these Gijmnosporangia, confined 

 to the various species of Juniperus, are merely the Teleuto-spore 

 condition of forms which when growing on certain species of 



* " Sitzungsber. cl. Bot. Yer. in Mimchen," Jan. 12, 1891, 



