10 



distinct organs, tiie root, stem, uiid leaves, very many plants show 

 no such specialization, but have all tlieir vegetative; functions per- 

 formed by the whole plant-body, which then needs no variety of 

 organs. Of the latter class of plants are the rockweeds and sea- 

 mosses, the fresh-water jJoiid-scums and the fungi, which are obvi- 

 ously much simpler and n)ore primitive plants than those with roots, 

 stems, and leaves. In all true fungi the plant-body consists of numer- 

 ous simple or branching white threads which spread over the surface 

 or through the substance of the object on which the fungus grows. 

 These threads constitute the so-called mycelium of the fungus, and 

 are comparable with the more elaborate plant-body of other plants, 

 since they perform all its vegetative functions. 



Equally important with its own healthy growth is the provision by 

 any plant or animal for the perpetuation of its kind, and to this end 

 it develops organs of reproduction. In many of those plants provided 

 with root, stem, and leaf, these reproductive organs are grouped into 

 a structure called a flower, and such plants are known as Flowering 

 Plants. They all produce, by the further development of certain 

 parts of their flowers, structures known as seeds, which can, under 

 favorable conditions, develop into new plants similar to that which 

 produced them. 



Fungi do not produce flowers, and they vary greatly in their repro- 

 duction, but they all agree in producing bodies called s2yores, much 

 simpler than seeds, as would be expected, Init analogous to seeds in 

 their ability to develop, under favorable conditions, into plants simi- 

 lar to those which produced them. These spoies are usually produced 

 on special fruiting or reproductive threads which grow from the veg- 

 etative threads of the mycelium of the fungns. The reproductive 

 threads may remain separate, thus producing their spores free in the 

 air ; or they may become interlaced or consolidated into a complicated 

 fruiting structure, on which the spores are produced either superfic- 

 ially or in cavities from which they finally escape into the air. 

 The spores of fungi, being so small and light, are readily taken up 

 and widely spread by currents of air, and are easily carried by 

 insects from plant to plant. In such ways a fungous disease may 

 spread from a single insignificant case until it becomes epidemic over 

 a large area. 



In the course of its life-cycle the ordinary foivering ■pkud passes 

 from the seed, through the seedling, to the adult plant bearing flowers 

 and then seeds like that from which it grew. Many of the fungi, 



