122 



PRACTICAL BOTANY. 



duction by zoospores or zoogonidia also occurs. The 

 plants of this class are found as parasites on algae ; some- 

 times also on Flowering Plants, and on animals and Fungi 

 which live in the water. Relationship can be traced 

 between members of this class and members of several of 

 the higher classes of Fungi. 



References for Reading. GoebePs " Classification of Plants," p. 85; 

 Vines' " Text-Book of Botany," pp. 285, 286 ; Bennett and Murray's 

 " Cryptogamic Botany," pp. 344-347 ; Carpenter's " The Microscope," 

 p. 565. 



CLASS IT. The Smut Fungi (Ustilaginece). The Smuts, 

 or Bunts, are parasites on various flowering plants. They 



are especially common on the 

 grasses, causing diseases which 

 are sometimes very destruc- 

 tive to the cultivated grasses. 

 The attack of the smuts is in 

 most cases confined to some 

 particular part of the plant, 

 as the leaf, the stem, or the 

 flower, on which they form 

 spots that are brown or yel- 

 low during the early stages, 

 but become black as the spores 

 ripen. In some cases the 

 smut spreads through all the 

 different parts of the plant. 

 The course of development of these Fungi, so far as it 

 is known, is believed to be as follows : The black resting 

 spore germinates into a promyceliuvi, a minute plant of 

 few cells. The promycelium bears male and female spo- 

 ridia; spores from these unite and the zygospore thus 

 formed develops into a mycelium; this mycelium produces 

 another crop of the black resting spores. The promyce- 

 lium is the gametophyte; the mycelium is the sporophyte. 



FIG. 64. Wheat bunt (Tilletia 

 caries) . (Kellerm au . ) 



