883 



THE OCCURRENCE OF AN INVERTED HYMENIUM 

 IN AGARICUS CAMPESTBIS. 



By G. p. Darxell-Smith, D.Sc, F.T.C. 



(Plates xoi.-xciii.) 



In 1917, some inuslirooiii-growers, who were growing mush- 

 rooms on a large scale in an old disused railway-tunnel, brought 

 to me, for examination, a number of mushrooms that were un- 

 saleable on account of their appearance. The mushrooms were 

 grown upon large beds of manure, the making of which I had 

 superintended. The manure was fairly moist, it was lightly 

 compacted, and the average temperature was 22''C. Both the 

 stipe and the cap of the specimens were somewhat tough. The 

 cap was quite unusual in appearance. Instead of having the 

 normal, comparatively smooth skin, its surface was broken by 

 one or mor^ black protuberances, 1*25 cm. or more in diameter, 

 that looked like boils (Plate xci., fig.l). It was this appearance 

 that spoilt the sale of the mushrooms. Samples of mushroom- 

 spawn from Sydney, from Adelaide, and from France, were grow- 

 ing in the same tunnel, and providing normal mushrooms; it was 

 only a particular sample of spawn imported from France that 

 was giving rise to these abnormal specimens. A close inspection 

 of the black protuberances showed that they were composed of 

 sinuous, labyrinthiform gill-lamellse (PI. Ixci., fig.2). They had 

 the appearance of small inverted caps, but no appearance of a 

 stipe could be found. Sections through the cap showed that 

 these structures were quite separate from the normal hymenium, 

 which was present on the undersurface of the cap (PI. xcii., fig. 3). 



Sections for microscopical examination were prepared and 

 stained. They showed that the structure of the hymenium on 

 the undersurface of the cap was quite normal. 



Sections through the hymenium on the upper surface of the 



