DIMORPHISM IN FUNGI. 131 



This fungus is called Eurothim herbarionwi, and was long con- 

 sidered to be quite distinct, and indeed a very different species 

 from Aspergillus glaiicus. Now, Aspergillus glaucus is considered 

 to be simply the conidial form of Eurotium. 



Another very good example is to be found in the Grass 

 Mildew. If rankly-growing grass in a damp position be examined 

 during the summer, it will very frequently be found covered with 

 white mildew. If this be examined under a power of 400 dia- 

 meters, it will be seen to consist of the usual mycelium, from 

 which spring large numbers of conidial chains, similar to those 

 already described, and so delicate that the slightest breath des- 

 troys their attachment. This was long known under the name of 

 Oidium itiojiiloides, one of the Mucedines. 



But in the autumn this same mycelium produces a little brown 

 conceptacle, just visible to the naked eye, which, when examined 

 with a low power of 100 diameters, is found to be surrounded 

 with radiating branches, and the interior is also found to contain 

 asci full of spores. This is the fungus known as Erysiphe gratnifiis, 

 and although formerly these two fungi were considered quite dis- 

 tinct, they are now known to be simply the conidial and perfect 

 stages of the same fungus. These brown receptacles do not set 

 free their spores during the autumn in which they have been 

 formed, but they fall to the ground with the decaying grasses and 

 rest on the ground all the winter, the hard, outer coat effectually 

 protecting the asci and spores. No sign of life can be detected 

 till the early summer, when these bodies burst and the spores fly 

 out into the air and are wafted in every direction, sometimes 

 absolutely throwing out spawn-threads as they sail about in the 

 air. Those that alight on Gramifia;, or grasses, attach themselves 

 by their spawn-threads, and immediately produce the Oidiwn over 

 again on their hosts. 



A third form of fructification has been described, viz. — pyc- 

 nidia, which are simply small conceptacles, containing spores, 

 after the nature of conidia. These are sometimes called stylo- 

 spores. 



Another Oidium — which is only the conidial form of another 

 fungus — is O. leucoconium, found' on rose-bushes. The whole of 

 the leaves of the bush are sometimes grey and shrivelled, from the 



