FUNGI INJURIOUS TO JUNIPERS. 69 



trees, learn to recognise the earliest stages of the disease, and if it 

 appear cut out the young patches and burn every trace of diseased 

 cortex. 



A subterranean fungus known as Rhizina undulata has lately been 

 found to be very destructive to young Larches, Silver Firs, and other 

 Conifers (e.y., Tsuya Mertensiana, Pseudotsuya Douglasii, Picea sitdiensis, 

 and Pinus SfrobusJ. It seems to belong or be related to the Pezizas, 

 An obscure group of fungi known aS Rhizodonia also still need 

 careful investigation.* 



It will probably be observed that I have followed no very strict 

 classification of the Conifers in this paper, 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 Cupressinese. 



IV. The Junipers. The most remarkable diseases of the Junipers are 

 those due to various species of a urediiious fungus known as Gymno- 

 x/><>rau(/iwii, 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 remarkable 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 Gyinnosporamjia^ confined to the 

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

 forms which when growing on certain species of Kosacese -e.fj-, Pear, 

 Hawthorn, Mountain Ash, Service-tree, etc. present a totally different 

 appearance ; these secidial forms on the Eosacese received the name of 



A number of careful experiments have been made iu this country 

 by Mr. Plowright, one of the best authorities in England on the 

 Uredinese, and he came to the conclusion that about four species of 

 Gymnosporanijiurn may be upheld as far as this country is concerned. 

 These species occur on /. Sabina and the pear ; /. Sabina and the 

 Hawthorn and others ; /. communis and Hawthorn, etc. ; and J. communis 

 and the Mountain Ash.f 



The results of such infection-experiments from various sides were to 

 arouse suspicions as to the autonomy of some of the species, though 

 some of the main points were confirmed by all. Credit is due to 

 Mr. Plowright for establishing the converse culture of the ^Ecidio-spores 

 on the Juniper, in the case of G. davarieforme. 



Recent experiments have raised the whole question of the species 

 of Gymnosporanfjia again, and I mention this here because it seems 

 to me of importance that the question should be settled, as it afTects 

 tin 1 cultivation of Pears, Apples, Hawthorns, and other Rosacese as 

 well as Junipers and other Conifers. 



Tubeuf says that if G. davariefomne is sown on Crataegus, it produces 

 Roestelia cornuta. On the Mountain Ash and on Cydonia vulgaris it 

 only goes so far as to produce spermogonia. On other hosts it grows 



* " Sitzungshericht des Botanischen Vereins in Miinchen," Jan. 12th, 1891. 

 t " British Uredineoe and Ustilaginese," p. 233. 



