SECT. in. PERONOSPOEA, 285 



it sometimes hardens the tissues of the potato, but 

 sometimes causes rapid and loathsome decay. 



The thread-like fibres of the spawn of the Peronospora 

 permeate even the branches and wood of trees. Wasps 

 are frequently seen to frequent hollow trees, probably in 

 search of the mycelia of some of these parasitic fungi, 

 which is identical in structure with the material of 

 which their nests are built. Signore Panceri, professor 

 of comparative anatomy in the university of Naples, has 

 discovered seven species of Mucedines in the albumen 

 of hens' eggs. 



Chemical changes in preserved animal and vegetable 

 substances afford suitable food for the Penicillia mould, 

 if indeed they are not the immediate cause of these 

 changes. The threads rising from the mycelium of 

 these moulds terminate in bundles of branchlets carry- 

 ing at their summits strings of spores, like necklaces of 

 small beads collected into bunches like tassels, white, 

 yellowish, blue or red according to their age or kind. 

 Figure 34 represents various species of Mucedines, in 

 which c is the Penicillium armeniacum, and / is a spore 

 of Helminthosporium Hoffinanni ; all are magnified. 

 Different species of the Penicillia form the blue and 

 brick-red moulds on cheese, and the greenish and grey 

 moulds on jam and preserved fruit. They appear as dry 

 rot, as orange coloured spots on long kept potatoes, as 

 mildew on cloth, silk, sugar, meat, and even on weather- 

 beaten window glass. They can exist in metallic and 

 poisonous solutions by decomposing the chemical com- 

 bination, rejecting the metal or poison, and living on 

 whatever nutriment may be found in the remainder. 

 Like the larger fungi, these minute plants are sometimes 

 poisonous; the fatal effects occasionally produced by 

 sausages and spoilt meat are supposed to be owing to 

 poisonous moulds. 



The Mucedines conform to the law prevailing in 



