172 AGARICACEiE Psalliota 



789b. P. xanthoderma W. G. Sm., Agaricus xanthodermus Genev. 

 (from the yellow-stained outer surface and flesh ; Gr. xanthos, 

 yellow, derma, skin) a. 

 P. fleshy, convex, even, greyish-white, becoming yellowish when 

 touched. St. stuffed to hollow, white, yellow at base. A. 

 membranous. G. sinuato-free, pale rose, becoming purple- 

 brown. Flesh becoming yellow. 



Pastures. Autumn. 3 J x 4 X § in. 



790. P. eretaeea Quel, (from its chalky-white colour; creta, chalk) 



a b c. 

 P. convexo-nattened, obtuse ; marg. even, rivulose or squamu- 

 lose. St. hollow, attenuate upwards, smooth. G. becoming 

 fuscous. Flesh unchanging white. 



Pastures, stoves ; rare. Feb. -Oct. 3§ X 4 X g in. Resembling 40. 



791. P. pratensis Quel, (from its habitat ; pratum, a meadow) a c. 

 P. expanded, obtuse, floccoso-farinose, then smooth, whitish, then 



greyish. St. hollow, colour as P. G. arcuate, brown. 



Taste and odour pleasant. Pastures, woods. Oct. 3J x 3 X § in. 



792. P. eampestris Quel, (from its habitat ; campus, a field or plain) 



a b c. 

 P. expanded, silky-even, sometimes squamulose, whitish. St. 

 stuffed, even or squamulose, whitish. G. crowded, bright 

 salmon, then umber-fuscous. Flesh white. 



Odour pleasant. May-Dec. 5 x 3! X I in. Variable in size and colour. 

 The common edible mushroom. Sometimes the flesh becomes faintly 

 reddish or brownish when cut or broken. Sometimes the odour is strong 

 and somewhat unpleasant. The following varieties have been described : 

 — 1. alba W. G. Sm., Agarictis eampestris L. var. albus Viv., P. silky- 

 white ; St. short. 2. praticola Magnus, P. rufous-squamukse ; flesh rufescent 

 when cut. 3. rnfescens W. G. Sm., A. eampestris L., var. raj esc ens Fr., 

 P. rufous-squamulose, St. long. 4. umbrina Magnus, P. at length even ; 

 umber. 5. fulvastera W. G. Sm., A. eampestris L., var. fidvaster Viv., 

 P. ochreous-tawny ; St. solid. 6. costata W. G. Sm., A. eampestris L., 

 var. costatus Viv., P. sulcate. 7. silvieola Magnus, P. smooth, shining ; 

 St. elongate, somewhat bulbous, hollow ; A. large. 8. elongata W. G. Sm., 

 A. eampestris L., var. elongatus Berk., P. at length even, shining-white; 

 marg. permanently appendiculate with veil ; St. elongate, bulbous. 

 9. exannulata W. G. Sm., A. eampestris L., var exannulatus Cooke, 

 A. fugitive or obsolete. The gills of cultivated mushrooms are frequently 

 thickened or obliterated by disease ; this is caused by a white parasitic 

 fungus, Mycogone pemiciosa. Diseased examples are not fit for food. Sound 

 examples of true mushrooms sometimes cause diarrhoea and sweating. 



792a. P. villatiea Magnus (from its frequent habitat, near houses in 

 the country • villa, a country house) a b. 

 P. convex then expanded, silky, soon squamose, ground pale 

 yellowish or brownish straw-colour then vinous-brownish ; sc. 

 vinous-brown. St. solid, somewhat ventricose, paler than P., 

 clouded pale vinous-brown. A. superior, large, tomentose 

 beneath. G. free, very crowded, not at first bright salmon, 



