FUNGI 311 



varying external appearance, and of a certain degree of differentiation of 

 tissue. This differentiation is exhibited in the formation of layers, some- 

 times pseudo-parenchymatous, adapted for special functions. They are 



FIG. 271. Section through sclerote of Sclerotima Sclerotioniin Lib., showing its cortical 

 medullary tissue (x 375). (After de Bary.) 



commonly characterised by the bearing of spores, or special spore- 

 mother-cells, on definite regions and in more or less definite arrange- 

 ment. They form, as a rule, that portion of the whole organism which 



FIG. 272. Simple sporophores of Phytophthora infcstans de By. a, formation of first 

 spores (zoosporanges) at ends of branches ; b, two ripe spores on each branch and a third 

 being formed (x about 200). (After de Bary.) 



is popularly termed a fungus, such as the stalk and cap of mushrooms, 

 the peridium of puff-balls, and the like. The structure of these is, as 

 has been said, very diverse, and it will be found described in more or 



