146 RESEARCHES ON FUNGI 



to the development of a red cell-sap in every cell. (5) In both 

 species, the spores are oval and deep black. ^ 



DifTerences between Coprinus comatus and Coprinus sterqui- 

 linus. — These species have been shown to agree in so many details 

 that it is not without interest to point out their differences, which 

 are of particular importance to field mycologists whose chief aim 

 is to differentiate closely-allied species from one another. These 

 differences, as shown by my own observations, are as follows : 



(1) As regards habitat. Coprinus comatus is not wholly copro- 

 philous. It occurs above turf in grassy fields, and above rubbish 

 including sticks which it is able to rot. The spores germinate on 

 sterilised horse-dung balls in crystallising dishes, and a dense my- 

 celium is produced ; but the mycelium remains sterile even at the 

 end of several months. Coprinus sterquilinus, on the other hand, 

 is wholly coprophilous and grows upon horse dung in fields and 

 gardens, etc. The spores germinate on sterilised horse-dung balls 

 in crystallising dishes and produce a copious mycelium which gives 

 rise to fruit-bodies in from four to five weeks. 



(2) As regards the colour of the stipe. In Coprinus comatus 

 the stipe remains white from first to last. In Coprinus sterquilinus 

 the stipe is at first white, but turns black or blackish at its upper end 

 during the ripening of the spores and the opening out of the pileus. 

 This blackening is not due to bruising, as Rea ^ erroneously states, 

 or to a spore-deposit. Bruising does not cause a stipe to blacken 

 at the place of injury. 



(3) As regards the size of the pileus and stipe. In Coprinus 

 comatus, just before expansion, the pileus is usually about 3 inches 

 high and may be as much as 4 inches high ; whereas in Coprinus 

 sterquilinus, at the same stage of development, the pileus is usually 

 only about 1 -5 inches high, sometimes only 1 inch, and never more 



^ In vol. i, p. 14, 1 stated that the spores of Coprinus comatus at first become pink 

 and then gradually turn black. This was a mistake. The spores are never pink. 

 The gills, it is true, turn pinkish and then black from below upwards. This pink 

 pigmentation, however, is not due to the change of colour in the spores but to 

 the development of a pink colouring matter in the cell-sap of all the cells of the 

 gills, basidia and paraphyses included. The spore-walls, on becoming pigmented, 

 pass through shades of brown to black. 



^ Carleton Rea, British Basidiomycetae, Cambridge, 1922, p. 500. 



