347 



In consequence of the microscopic minuteness of the spores their 

 Yolume and weight is very small as compared with the size of 

 their surface, and from this reason they are exceedingly sensitive 

 to air movements. Everybody who has laid the cap of a mush- 

 room on a paper for collecting the falling spores knows that even 

 in a room, the doors and windows of which are fuUy closed, so 

 that there is a practical stillness of the air, the spores do not drop 

 right verticall}^ but sail like a down more or less sidewise so that 

 the deposited spores give only a blurred picture of the gills or 

 pores or spines unless a small dish or the like is placed bottom 

 up over the fungus so as to still more prevent movements of the 

 air surrounding the dropping spores. 



From this we understand that the wind will catch the falling 

 spores and bring them far away from their native place, and that 

 the thick and uniform spore layer covering the upper side of PoL 

 applanatus etc. thus can not have been deposited during wind but 

 only in calm or nearly calm weather. 



It is perhaps not unreasonable to suppose that from the ground 

 heated during a hot day arise during a following cold and calm 

 night upwardly directed air currents, which, though very feeble and 

 perhaps not perceptible to our senses, yet are strong enough ta 

 force the falling spores upwards, so that these are caused to hover 

 in the air above their native place a more or less long while ere 

 they are allowed to fall again and land on the upper side of objects 

 iying in their way. 



With such a supposition the occurrence on the upper side of 

 Polypori and other Hymenomycetes of spores exactly like those 

 generated in the hymenium on the underside of said fungi is conceivable 

 without resorting to the »conidia»-theory. Such a supposition ex- 

 plains also the occurrence of said spores on adjacent or superposed 

 objects, which is incomprehensible, if we adhere to said theory. 



Here some one might remark: if the spores are so light and easily 

 moved even by the slightest movement of the air, why do they 

 remain on the object, where they land, and are not blown away 

 by the first next breeze? 



The answer is: the living spores adhere pertinaciously to the 

 surface with which they come into contact. Ash or other dry 

 powder strewed on a dry glass-plate you can easily blow away, 

 but if you catch on the same glass-plate the spores dropping from 

 a mushroom, you are unable to remove them by blowing. I do 



