HABITATS. 239 



and like them are found on decaying vegetable substances, old 

 stems of herbaceous plants, dead twigs, wood, stumps of trees, &c. 

 The exceptions are in favour of such species as Torula sporendo- 

 nema, which is the red mould of cheese, and also occurs on rats' 

 dung, old glue, &c, and Sporendonema Muscw, which is only 

 the conidia of a species of Achlya. One species of Bactridium 

 is parasitic on the hymenium of Peziza, and JSchinobotryum 

 atrvm, on the flocci of black moulds. 



In the other section of Coniomyeetes the species are parasitic 

 upon, and destructive to, living plants, very seldom being found 

 on really dead substances, and even in such rare cases un- 

 doubtedly developed during the life of the tissues. Mostly the 

 ultimate stage of these parasites is exhibited in the ruptured cu- 

 ticle, and the dispersion of the dust-like spores; but in Klletia 

 caries, Thecaphora hyalina, and Puccinia incarcerata, they remain 

 enclosed within the fruit of the foster-plant. The different 

 genera exhibit in some instances a liking for plants of certain 

 orders on which to develop themselves. Peridermium attacks 

 the Coniform; Gymnosporangium and Podisoma the different 

 species of Juniper; Melampsora chiefly the leaves of deciduous 

 trees ; Pcestelia attaches itself to pomaceous trees, whilst Qra- 

 pliiola affects the Palmacew, and JEndophyllum the succulent 

 leaves of houseleek. In JEcidium a few orders seem to be more 

 liable to attack than others, as the Composites, Ranunculacece, 

 Legmninosas, Lahiatm, &c, whilst others, as the Graminacece, 

 JSricacem, Malvaceae, Crueiferas, are exempt. There are, never- 

 theless, very few natural orders of phanerogamous plants in 

 which some one or more species, belonging to this section of the 

 Coniomyeetes, may not be found ; and the same foster-plant will 

 occasionally nurture several forms. Recent investigations tend 

 to confirm the distinct specific characters of the species found 

 on different plants, and to prove that the parasite of one host 

 will not vegetate upon another, however closely allied. This 

 admission must not, however, be accepted as universally appli- 

 cable, and therefore it should not be assumed, because a 

 certain parasite is found developed on a special host, that it is 

 distinct, unless distinctive characters, apart from habitat, can be 



