248 



RESEARCHES ON FUNGI 



Comparison of the Sizes of Wind-borne Spores in Asco- 

 mycetes and Hymenomycetes. The size of wind-borne spores, 

 which is so important a factor in determining their rate of fall, 

 is doubtless adapted to the spread of the spores by such air- 

 currents as ordinarily occur above the surface of the ground. 

 In this connection it is a distinctly interesting fact that although 

 Ascomycetes produce and then liberate their spores into the air 

 in a very different manner to that of Hymenomycetes, yet in 

 both groups of fungi the order of magnitude of the wind-borne 

 spores is the same. Evidence supporting this statement is given 

 in the following Table, where the sizes of the spores of a few 

 Ascomycetes which make use of the wind for dissemination 

 are compared with the sizes of the spores of a few well-known 

 Hymenomycetes. In each series the spores are arranged accord- 

 ing to the magnitude of their short diameters. This arrange- 

 ment has been adopted because the rate of fall of spores, and 

 therefore the ease with which they can be transported by air- 

 currents, is chiefly determined by the size of their short diameters 

 and not by that of their long diameters, since spores tend to fall 

 with their long axes in a horizontal position. 1 The unit of measure- 

 ment is I fj,. The sizes of the spores of the Ascomycetes are those 

 given by Massee. 2 The sizes of the spores of the Hymenomycetes 

 were measured by myself and are taken from the Table in Part I., 

 Chapter XIV. 



Comparison of the Sizes of Spores. 



1 Cf. the end of Chap. XV., Part I. * G. Massee, British Fungiis Flora, vol. iv. 



