28 A HMMKTKIC STUDY (»F TIIK (,oMi)| \, ETC., 



differentiated by a simple Biometi'ic method. It has been 

 found possible to determine the mode of origin of such a 

 mass of free conidia from their co-efficient of variability. 



VARIATION IN SPORE MEASUREMENTS. 



It is usual to include in the diagnoses of fungi mea- 

 surements of their mature spores, and it is not uncommon 

 to find different authorities quoting different figures as 

 diagnostic characters of one and the same species. 



The following measurements for the length of the 

 spores of Coprivns comatus, Fries, are taken from publica- 

 tions by the eminent authorities given below: — 



COPRINUS COMATUS, Fries. 



W. G. Smith 18,u. 



G. Massee 15^. 



M. C. Cooke 14ju. 



R. Buller 12.0 



M- 



Britzelmayer 12,u -14 n. 



Karsten 11m -13 ^i/. 



This lack of uniformity in the published measurements 

 led Massee (i) to re-examine many of the types preserved 

 at Kew. Although a useful character for the differentiation 

 of various species, the size of fungus spores is subject to 

 considerable variation. Buller (2) gives an intere.sting ac- 

 count of differences in form and size of the spores of 

 Amanatopsis vagivatus, Bull. 



Some time ago, when measuring the dimensions of 

 conidia produced by a Clodosporiuvi (3) occurring on wheat, 

 a considerable range of variation was noted. A consider- 

 able number were measured very cai'efully, with the object 

 of determining the limits of size, in order to prepare an ac- 

 curate diagnosis of the species. Records of several other 

 species were subsequently made. (•) From a casual study 

 of these records it became apparent that in certain species 

 wide variations may occur, whilst in others the range of 

 variation determined was within narrow limits. This ulti- 

 mately led the writer to make a really critical examination 

 of two common .species, with interesting and unexpected re- 

 sults, which are here presented. 



(1) MiufMcc, (I. •"Grcvillcn," Vol. 21. p. 77. 



(2) Riillor, It. "Rournrrh«i« on FuriKi." 



(3) CladoHporiutn uraminum, ConlBz^Srolecolrichiim pramxtiuTn, 

 Fuchcl. 



(4) Vulvaria Kjtcciota, Peziza vcticulona, RhitopuH viariranit, Fxisarium 

 up. 



