HABITATS. . 239 



nnd like tlicm 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 011 rats' 

 dung, old glue, &c., and Sporcndonema Musca, which is only 

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

 ia parasitic on tho hymcnium of Pcziza, and JEckinobotryvm 

 atrum, on the llocci of black moulds. 



In the other section of Coniomycefes the species are parasitic 

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

 on really dead substances, nnd 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 Tilletia 

 caries, Thccapliora Iiyah'nu, and Puccinia incarccrata, they remain 

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

 genera exhibit in some instances a liking for plants of certain 

 orders on which to develop themselves. Peridcrmium attacks 

 tho Conifer &; Gymnosporaitgium and Podisoma the different 

 species of Juniper; Hclamptora chiefly the leaves of deciduous 

 trees ; JitrsleJia attaches itself to pomaccous trees, whilst Qra- 

 pfiiola affects the Palmacca, and EndopJnjllum the succulent 

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

 liable to attack than others, as the Compo 'la t Ranunculacea, 

 Lcyuminoscc, Labiata, cvc., whilst others, as the Graminaceae, 

 Ericaceae, Mfalcaccat, Cntcife.ra, 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 

 Coniomyccf.es, 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, hcwevcr, 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 bo 



