404 RESEARCHES ON FUNGI 



inch to be what we have calculated, this particular mushroom must 

 have produced a total of 18,218,687,000 spores. 



As a result of the investigation just described, it may be stated 

 in round figures that a wild mushroom, with a pileus about 4 inches 

 in diameter, possesses a hymenial area of about 1 33 square feet, 

 which contains about 4,000,000,000 basidia which discharge about 

 16,000,000,000 spores. There can be no doubt whatever that 

 every large wild mushroom which develops in a normal manner 

 liberates upwards of 10,000,000,000 spores. 



The Mushroom and the Panaeolus Sub-type. The gills of Psalliota 

 campestris possess all the general characters which have been 

 described for the Aequi-hymeniiferous Type of organisation : the 

 gills are wedge-shaped in cross-section and positively geotropic, 

 the hymenium everywhere looks more or less downwards toward 

 the earth, and every small part of the hymenium (every square 

 mm.) produces and liberates spores during the whole period of 

 spore-discharge. The gills also exhibit all the characters which 

 have been enumerated for the Panaeolus Sub-type, as is indicated 

 superficially by the mottling of the hymenium, which differs in no 

 essential point from that of Panaeolus campanulatus or Stropharia 

 semiglobata. 



Text-book Illustrations of the Hymenium. For several decades 

 Sachs' figure of a cross-section through the gill of a Mushroom has 

 been considered sufficient by many text-book writers as an illus- 

 tration for the hymenium of the Hymenomycetes in general. It 

 has been copied from book to book and is familiar to every botanist. 

 Sometimes it has been plagiarised, but slight alterations for the 

 worse do not always prevent one from detecting its original source. 

 Sachs' figure has done excellent service : it has enabled students 

 to realise at a glance some of the main facts in gill-structure ; 

 it teaches that the hymenium, subhymenium, and trama are 

 differentiated from one another, and that in any section through 

 the hymenium two kinds of elements may be distinguished, namely, 

 those which bear spores and those which do not ; and, finally, it 

 represents fairly correctly the shapes of the various cells, more 

 especially those of the basidia with their club-shaped bodies, their 

 sterigmata, and their oval spores. However, when one comes to 



