xxv.] CORN MILDEW AND BARBERRY BLIGHT. 195 



cases might be added. Another instance is met with in 

 the Sclerotium, which produces Peziza tuber osa, Bull ; this 

 is generally found in company with the black, hori- 

 zontal rootstock of Anemone nemorosa, L. At one time a 

 relationship was suspected. Plant-lice and fungi often 

 consort curiously together. Passarini has said that the 

 Aphis, named Rhopdlosiphum dianthi, Sch., gives rise to a 

 kind of mould on greenhouse plants which the French 

 name Fumagine. This is the dark-coloured fungus named 

 Fumago by botanists. A fungus which is extremely 

 common on evergreens in Britain, named Capnodium 

 Footii, B. and Desm., is almost invariably accompanied by 

 the lichen, named Strigula Babingtonii, B. A coccus is also 

 almost constantly present with the fungus and the lichen ; 

 perhaps the former, by piercing the leaves or by leaving 

 some secretion from its body, prepares the way for the 

 fungus and its companion lichen. In the same way as the 

 jackal is sometimes termed " the lion's provider," so the 

 coccus may be the provider for the Capnodium or Strigula. 

 When the fungus and the lichen have once fixed them- 

 selves on the coccus-invaded plant, the host soon dispenses 

 with the service of the coccus. It may possibly yet be 

 shown that the germinating ^cidio-spore is the provider 

 for the Uredo, or the germinating Puccinia-spore the 

 provider for the sEcidium. 



Some rustics believe that mushrooms spring from salt, 

 because "experience has taught the practical farmer" 

 that a dressing of salt over a non-productive pasture will 

 generally cause a good crop of mushrooms to appear. The 

 result in this instance, however unvarying, does not prove 

 genetic relationship. 



In some instances the occurrence of Puccinia and JEci- 

 dium must of necessity be a mere case of consortism, as 

 in the familiar example of the parasites of Allium ursinum, 

 L., and A. oleraceum, L. In this instance we have an 

 sEcidium, a Uredo, and on the Continent (but not in 

 Britain) a Puccinia, named P. allii, Rud., all on the 



