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A TEXT-BOOK OF BOTANY 



fertilization, however, a structure called the spore-fruit is 

 developed. These spore-fruits appear on infected leaves as 

 minute dark dots (Fig. 134), each one being a sphere of 



heavy- walled cells (Fig. 135, 

 B), which usually bear hair- 

 like appendages of various 

 forms. In fact, the spore- 

 fruit is a heavy protecting 

 case for spores, and carries 

 mildews through the winter 

 or the dry season. The ap- 

 pearance of a many-celled 

 spore-case as the result of 

 fertilization, rather than a 

 new mycelium, suggests the 

 similar result of fertilization 

 among the red Algae ( 75). 



By bursting the wall of 

 this spore-fruit, one or more 

 delicate bladder-like sacs are 

 extruded, and through the 

 transparent wall of each sac 

 several spores may be seen 



(Fig. 135, B). The delicate sacs are called asti (singular, 

 ascus),a, word meaning "sacs," and hence the great group 

 of Fungi represented here by the mildews is named the 

 Ascomycetes, which means "sac Fungi." In the life-history 

 of the mildews it is evident tfrat there are two kinds of 

 asexual spores : those produced in chains by the sporophores, 

 and those produced in the sacs of the spore-fruit. Both 

 produce new mycelia, the latter starting the first mycelia 

 of the growing season, and the former multiplying mycelia 

 throughout the growing season. 



83. Other Sac Fungi. The group of sac Fungi is a very 

 large one, containing many forms that are well known and 



FIG. 135. Reproduction of mildew: 

 A , chain of spores developed by a 

 sporophore; B, spore-case burst, 

 and showing the extruded sac 

 (ascus) with its spores. After 

 TULASNE. 



