26 DISEASES OF FIELD & GARDEN CROPS. [CH. 



expansion at the top about lialf-an-incli across. On closely 

 observing these expanded tops in sunlight, especially when 

 held in favourable positions, as against a black background, 

 a slight sudden cloud resembling a puff of smoke or steam 

 may be seen to gradually sail away through the air from 

 the top surface. This almost invisible cloud really con- 

 sists of millions of minute spores, in this instance techni- 

 cally termed sporidia for a reason to be mentioned imme- 

 diately. 



The whole interest of the fungus now centres on the 

 expanded top, and especially to its surface, whence the 

 clouds of sporidia sail away. If we cut one of the cups 

 in two, and look on the cut surface with a magnifying 

 power of five, and twenty diameters, we shall see the 

 structure as shown at A and B, Fig. 7. We now notice 





FIG. 7, 



Peziza postuma, B. and W. Section through cup. 

 Enlarged 5 and 20 diameters. 



that the whole of the upper stratum of the expanded top 

 consists of elongated perpendicular cells as illustrated, 

 whilst the under surface is a mass of spherical cells of 

 various sizes ; but to see this curious structure well a 

 much higher magnifying power is required, and a small 

 fragment only of the top must be examined in section, as 

 at Fig. 8, magnified 400 diameters. We now distinctly 

 see the basal stratum of transparent globular cells of 

 various sizes, and a few of the hundreds of thousands of 

 vertical transparent bladders forming the top stratum, 

 and from which the cloud of dust consisting of oval trans- 

 parent sporidia arises. With a lancet we will now remove 

 a few of these vertical asci or long bladders, and magnify 



