240 m FUNGI. 



detected. JEcidium compositarum and sEciJium ranunculuccaritm, 

 for instance, are found on various composite and ranunculaceous 

 plants, and as yet no sufficient evidence has been adduced to 

 prove that the different forms are other than varieties of one or 

 the two species. On the other hand, it is not improbable that 

 two species of JEcidiwn are developed on the common berberry, 

 as De Bary has indicated that two species of mildew, Puccinia 

 graminis, and Puccinia slramtnis, arc found on wheat. 



HYPHOMYCETES. The moulds are much more universal in their 

 habitats, especially the Miicedines. The Isariacei have a pre- 

 dilection for animal substances, though not exclusively. Some 

 species occur on dead insects, others on decaying fungi, and the 

 rest oil sticks, stems, and rotten wood. The Stilbacci have also 

 similar habitats, except that the species of lllosporium seem to be 

 confined to parasitism on lichens. The black moulds, Dematici, 

 are widely diffused, appearing on herbaceous steins, twigs, bark, 

 *and wood in most cases, but also on old linen, paper, millboard, 

 dung, rotting fruit, &o., -whilst forms of Oladcsporium and ]\Iacro- 

 sporium are met with on almost every kind of vegetable substance 

 in which the process of decay has commenced. 



Mucedines, in some instances, have not been known to nppcar 

 on more than one kind of matrix, but in the far greater number 

 of cases they flourish on different substances. Aspcrgillus 

 glaucus and Penicill\um crustacciim are examples of these uni- 

 versal Muccdines. It would be far more difficult to mention 

 substances on which these moulds are never developed than to 

 indicate where they have been found. With the species of 

 Peronospora it is different, for these are truly parasitic on living 

 plants, and, as far as already known, the species are confined to 

 certain special plants, and cannot be made to vegetate on any 

 other. The species which causes the potato murrain, although 

 liable to attack the tomato, and other species of Solanaccte, does 

 not extend its ravages beyond that natural order, whilst Pero- 

 nospora parasitica confines itself to cruciferous plants. Ono 

 species is restricted to the Umbcllifcra:, another, or perhaps two, 

 to the Leguminosas, another to Rubiacca, two or three to Ramtn- 

 culacea, and two or three to Caryophyltacea. All the cxpcn- 



