GYMNOSPORANGIUM. 



391 



6h/mnosporangium juniperinum L. and G. iremelloides Hart, from 

 twigs and needles of Juniperus comTmcnis produced : 



On Host-plant. 

 Pyrus (Sorbus) Aucuparia, 

 Aronia rotundifolia, 

 Pyrv,s Malus, 

 Pyrus (Sorbus) Aria, 

 Cydonia vulgaris, 

 Pyrus (Sorbus) Aucuparia, 

 Pyrus Malus, - 

 Amelanchier canadensis, 

 Pyrus (Sorbus) Aria, 

 Pyrus Malus, 



Pyrus (Sorbus) Chamaemespilus, 

 Mespilus macrocarpa, 

 Pyrus communis, 

 Pyrus (Sorbus) Aria, 

 Pyrus (Sorbus) Aria x Chamae: 

 Pyrus Malus, - 



Pyrus (Sorbus) Chamaemespilus, 

 Pyrus (Sorbus) Aucuparia, 

 Aronia rotundifolia, 

 Pyrus (Sorhcs) torminalis, 

 Crataegus Pyracanthd, 

 Cydonia vulgaris, 

 Pyrus Malus, 



Formation of pycnidial spermogonia always precedes that 

 of aecidia. 



This fungus is of practical import on account of its occurrence 

 on leaves of apple-trees. Its attacks may be very virulent 

 and widely distributed. Eriksson mentions that near Stockholm 

 it is common on apples, and so virulent that many trees have 

 every leaf studded with Roestelia. (American apple-trees suffer 

 from Roestelia pirata, the aecidia of Gh/mnosporangium macroptcs 

 and other species. See p. 402.) 



Gymnosporangium juniperinum (L.) (G. conicum Hedw.) 

 (Britain and U.S. America). This species, also frequenting 

 Jtmiperiis communis, is distinguished by its shorter spores, 

 which, as Dietel pointed out,^ have a colourless papilla over 

 each germ-pore. The teleutospores are found on both twigs 

 and needles, on the former, however, they are much smaller 



pycnidia and spots only, 



Rostelia penidllata, 



Eostrup. 



^ Forstlich-naiurwiss. Zeitschrift, 1895, p. 378. 



