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Rh neighbourhood of Brickhill and Burnham, an extremely large number of species are to be found. They are necessarily very uncertain in appearance, depending as they do so much upon climatal influences, so that a long period is required before a district, even of limited dimen- sions, can be said to be exhaustively explored. Their occurrence depends to so great an extent upon the higher forms of life, for instance upon the proper quantity of dead wood, decaying vegetable matter or the like, and in few, if any, instances is food obtained directly from the soil.

Space will not allow of anything like a complete list, even of the species known to grow in the county, being given here, but in passing we may mention that the genera Amanita, Russula, Agaricus and Boletus are well represented. The poisonous A. muscarius is often very common in Black Park, at Wilton Park and Dropmore, and the even more poi- sonous A. phalloides occurs near Princes Risborough, where Tricboloma spermatica is also found ; Lepiota vittadini has been found near Bledlow ; Clitocybe dealbatus and C. laccatus at Burnham ; Collybia esculenta at Lane End ; Clitopilus prunulus near Halton ; Hebeloma crystallina, H. geophila and H. concentrica at Brickhill ; Coprinus micaceus and C. atramentarius on the rubbish heaps near Iver ; Lactarius piperatus, L. deliciosus, L.fuliginosus near Halton ; Russula nigricans, Brickhill ; R. emetica, R. ocbroleuca, R. alutacea, and R. rubra about Black Park ; Cantharellus cibarius near Farnham ; Boletus luteus, B. luridus, B. edulis, B. flavus, at Brickhill, etc. ; Fistulina hepatica, Wilton Park ; Hydnum auriscalpium, Marlow woods ; Hirneola Auricula-Judæ, near Wycombe ; Phallus impudicus, very common in the Chiltern woods, and in 1902 especially frequent in a wood near Amersham, also in the Brickhill pine woods ; the puff ball Lycoperdon giganteum, and the smaller members of the genus, as L.gemmatum, saccatum and pyriforme, have been noticed about Brickhill. The pretty Cyathus vernicosus was found near Buckingham. The ' rusts, smuts, mildews and moulds,' which in some instances are such deadly foes to the agriculturists, market garden- ers, or horticulturists, are too well represented. As an instance of leaf- fungi one may draw attention to a common example in the sycamore, where the unsightly black patches on the leaves in the autumn are caused by the fungus Rhytisma acerinum ; another is the well known wheat rust (Puccinia graminis), one of the pests which it is said is referred to in the Old Testament. For many ages it was supposed to be connected with the occurrence of the barberry (Berberis vulgaris), and edicts were promulgated to destroy the plant in certain countries, but the botanists of the early part of the nineteenth century proved to their own satisfaction that the barberry could not have this malevolent influence, since the fungus which grew upon it was a different species from that which was found upon the wheat, the former being Æcidium Berberidis, the latter Puccinia graminis, in fact belonging to two different genera. It was however reserved for De Bary to prove that these two widely differing fungi were really only two different stages in the life history of a single individual species, and demonstrated it by sowing the aecidiospores of the barberry upon the