!g REPRODUCTION 



duced. Of such a type is the ordinary smut of cereals ; the spores 

 of the fungus germinate with the germination of the grain and en- 

 ter the young plant as it emerges from the seed. Little, if any 

 ti;ace of its presence can be discovered until the grain comes to 

 form its spike or panicle, when in place of ovaries the black 

 smutty spores of the parasite are developed. 



3. That of external parasites that form mycelium on the surface 

 of leaves or fruit, penetrating the exterior cells for purposes of 

 nutrition. Such are the powdery mildews which form cobwebby 

 or powdery patches on many leaves as those of roses cultivated 

 in greenhouse, lilacs, dandelions and many cultivated plants. 

 Such too are the black forms of Meliola found on leaves in trop- 

 ical and warm temperate regions. 



Certain parasitic fungi are peculiar to the host on which they 

 dwell ; other parasites seem to thrive equally well on a variety of 

 hosts. In some instances, the species of certain fungus genera 

 affect certain genera or allied genera of the higher plants. The 

 Leguminosae, e, g., are parasitized by rusts belonging to the genera 

 Uromyces and Ravenelia, tho species of the first genus occur on 

 other plants ; the apples and haws (Pomaceae) by the various 

 species of Roestelia ; the pines and spruces by the species of 

 Periderniium ; the roses, brambles ard Potentilleae by the species 

 of Phragmidimn ; the Ericaceae by species of Exobasidium ; Juni- 

 pems and Cupressus by the species of Gymnosporangium. 



As a tentative arrangement we may recognize among the 

 fungi : (i) A group of plants of simple structure in which the 

 algal characteristics including sexual methods of reproduction 

 are still manifest, and (2) A higher group in which a more com- 

 plicated structure is commonly associated with a loss of sexual re- 

 production ; as these higher forms manifest two marked methods 

 of spore production, (a) Those enclosed in sacs or asci (PL f, 

 f. //), and (b] Those developed free on enlarged basidia (PL /, 

 f. /(?), we may recognize three convenient classes of fungi as fol- 

 lows : 



1. PHYCOMYCETES (the lower or algal fungi). 



2. AscoMYCEfES (the sac-spore fungi). 



3. BASIDIOMYCETES (the basidial spore fungi). 



In the first group sexual reproduction is common. In the 



