6 INTRODUCTION. 



cells called basidia or enclosed in elongated sacks or asci — 

 corresponding to exogens and endogens in the phaenogamia 

 plants. 



Structure. — There is no class of plants where there is so 

 great a variety in structure as in the fungus class. It is true 

 they are all cellular, but differ in biological structure from 

 merely a mass of slimy myxogaster to a hard and ligneous 

 polyporus. 



There is so great a variety in structure of the different 

 groups that it cannot be compressed within this introduction ; 

 even in the common mushroom family there is such a vast 

 difference in structure as to make it a part of the differential 

 character, such as the ephemeral Coprinus growing on manure 

 heaps to the fairy ring Marasmius, which, when dry and 

 shriveled, will revive again to its original structure. Beside 

 the general tissue of which fungi are composed there exists in 

 a genus of Agaric a class of distinct vessels which carry a milky 

 fluid. They exist in all parts of the plant, especially in the 

 softer parts ; the genus is called Lactarius — the fluid is differ- 

 ently colored, mild or acrid. In many fungi something 

 distinct from the cellular tissue seems to exist, in the form of 

 a viscid or glutinous fluid which clothes the surface of the cap 

 of agarics, more conspicuous during wet and damp weather. 

 This secretion forms a good specific character, since it is always 

 present in the same species. The structure of the different 

 parts of a fungi is not always homogeneous ; the cap of an 

 agaric is generally more spongy than the stem, so are the gills 

 or plates which may be waxy or watery in certain genus and 

 heterogenous in structure with the rest of the plant. The gills 

 of some species are deliquescent, forming a good generic 

 character. 



Forms. — The forms which these singular plants assume are 

 extremely diversified. In some instances they are shaped like an 



