144 YORKSHIRE NATURALISTS UNION. 



988. Boletus cpassus Mass. 



N.E. — Scarboro'. Under trees in pastures. Resembling 

 7j. edulis superticiall}-, hut distinguished by the absence of a 

 network of raised lines on the very stout stem, and in the 

 flesh changing from white to primrose-yellow when cut. 

 989. — Boletus satanas Lenz. Poisonous. 



N.E. — Raincliffe Wood, Scarboro'. 



N.W.— Helmsley (*Nat., Sep. '84). 



S.W. — Huddersfield (F.F., '95). In mixed woods. 



A very beautiful fungus with a whitish pileus, blood-red 

 pores, and a stout, orange stem covered upward with a network 

 of blood-red raised lines forming a network. 



990. — Boletus lurid us Schar-ff. Poisonous. 



S.W. — H.\. 1788. (Bolton, Tab. 85). Frequent: recorded 

 for all the county divisions excepting N.W. 



Flesh yellowish, but instantly changes to a deep blue when 

 cut or broken. This changing of the flesh to a blue colour 

 when broken and exposed to the air is possessed in a more or 

 less marked degree by many species of Boletus, and depends 

 on the presence of two distinct substances in the flesh of the 

 fungus : one of these is a resinous substance that becomes 

 blue in contact with ozone ; the other is a substance soluble 

 in water, which concentrates or ozonises the oxygen of the air, 

 and then combines with the resinous substance to which it 

 gives up its oxygen in the form of ozone, the result being a 

 blue colour. 



991. Boletus puppureus Fr. 



S.\\'.- Heaton Woods near Bradford' (Lees' Fl.). 

 992. — Boletus rubinus W.G.Sm. 



N.E. — Scarboro', under trees on the racecourse. 



Mid W\— Bolton Woods (Nat., Feb. '86). 



S.W\— Heptonstall (Fl. Hx.). 



The only Boletus having the tubes red throughout their 

 entire length. 



993. — Boletus felleus Bull, l^oisonous. 



S.W. — Frequent ; records many. 



Trans. V.N.U., 1904 (pub. 1904) Bot. Series. Vol. C. 



