The Relation of Fungi to Other Plants 



Threads 



Bread mould (mag- 

 nified) 



lost their power of constructing such food, and also their green 

 granules by which this worit of construction may be carried on. 

 The life history and structure of fungi 

 has been studied so minutely that one is spore cases , 

 able to arrange them in three well- 

 marked classes: 



The first class, the algal-like fungi 

 (Phycomycetes), includes bread moulds 

 and several of those fungi which cause 

 diseases of plants and animals — the 

 downy mildew on the grape, the potato 

 rot, the common white mould which 

 fastens dead flies to the walls or window 

 panes in the autumn, and the fungus 

 which grows on salmon 



and causes them to die in great numbers. The 

 plant of these fungi is cobwebby, sometimes 

 growing within the cells of the plant substance on 

 which it lives, and sometimes growing both 

 within and on the surface. A freshly moulded 

 piece of moist bread shows the bread covered with 

 exquisitely fine transparent threads, which con- 

 stitute the plant. Later, spore cases containing 

 tiny black spores will be seen, which give a del- 

 Spores borne in del- icate gray tint to the plant at first, but later form 

 icate membran- ^ black, repulsive mass as their numbers increase. 

 These plants are regarded as descendants of de- 

 generate algse, which lost their power of inde- 

 pendent existence through stealing their food 

 instead of making it for themselves. 



The second class, the spore-sac fungi, 

 produce their spores in delicate membranous 

 sacs. The spore-sac fungi vary greatly in 

 size, habit, and structure. Most of them 

 are inconspicuous members of the plant 

 world, as the yeast plant, by which our 

 bread is raised ; the fungus which causes 

 the peach leaves to curl and the black knots 

 to appear on cherry and plum trees. 



The third class is made up of all fungi which bear their 



9 



ous sacs (magni- 

 fied) 



Spores borne on little 

 spicules (magnified) 



