Page:Coloured Figures of English Fungi or Mushrooms.djvu/690

 Heathfield, who found it succeed. I now may, therefore, venture to give my opinion.

By my advice, Lord Heathfield caused proper passages for the admission of common dry air, which became an effectual cure, and, I persist in it, that where there is a certain proportion of dry air, these Fungi are not to be found, but only in those seasons when such is natural to the climate. They indicate a certain temperature, like a thermometer, pointing it out when we otherwise do not perceive it; and we may be assured, that a certain degree of moisture and temperature is as necessary for the growth of the Fungus tribe, as any other. The ancients were aware of the effects of certain winds being more or less wholesome; and the architects advised the buildings in the streets to be placed accordingly; and when foetid lakes or any other reasons occurred, to avoid the ill effects with what care they could.

Tab. 409. On June 17, 1807, John Walker, Esq. sent me specimens of the leaves from some wall trees, at his seat at Southgate, on the surface of which grew the present parasite. It covered nearly in this manner a large number of trees. The individual leaves did not appear much affected around it. The yellow margin of the Fungus succeeding the green of the leaves, passes into an orange-colour, on which are numerous bluntish conical projections, often emitting from their centre an orange substance, of a jelly-like appearance, and looking very much like little volcanos; some seem riper, and are nearly black, and the substance at the mouth appears decayed and whitish; and from the transverse section we might suppose them to belong to the Genus Sphæria, the inside filled more or less with this substance, forming, from the centre in the upper half of the leaf, while the cuticle and cortex forms the orange or black conical covers; the under side of the leaf is apparently perfect and not at all disturbed. Mr. Walker had the leaves stripped from the trees.