Survey of Plant Kingdom 125 



(1) Class Phycomycetes. — The algalike fungi of the class Phyco- 

 mycetes (fi ko mai -se' tez) (Gr, phykos, algalike; mycetes, fungi) consist 

 of filamentous hyphae, with organized nuclei but usually without septae 

 (cross walls). The threadlike hyphae (hi'fe) (Gr. hyphe, web) fre- 

 quently form a web known as the mycelium- (mi -se' li um) (Gr. mykes, 

 fungus). Members of this class are common saprophytes^ some living in 

 water. Young hyphae may be branched, nonseptate, and contain numer- 

 ous nuclei. Older hyphae, especially during sexual reproduction, may 

 show septae. Rootlike rhizoids {yV zoid) (Gr. rhiza, root; eidos, form) 

 may absorb materials from the substratum and anchor the plant. Spo- 

 rangiophores (spor-an'ji for) (Gr. sporos, spore; anggion, vessel; 

 pherein (to bear), bear spore cases called sporangia in the species which 



-Nucleus 



-CytopJa5^m__ 

 - -Vacuole ' 



--Aucleus 



-Vacuole 

 -Cytoplasm 



Fig. 37. — Bread yeast (Saccharomyces cerevisiae) of the phylum Eumycophyta, 

 class Ascomycetes. A, Yeast cell; B, three stages showing reproduction by budding 

 (asexual) ; C, yeast cell which under certain conditions will develop an ascus (Z)) 

 with its ascospores (£). A new yeast cell will develop asexually from each 

 ascospore. 



are not aquatic. The air-borne, nonmotile, asexual spores germinate to 

 form new hyphae. In aquatic species, .such as Saprolegnia, motile zoo- 

 spores are formed in zoosporangia. Sexual reproduction may occur by 

 isogamy or heterogamy, depending upon the species. The sexual method 

 is known as conjugation and takes place between two different filaments 

 (as in Rhizopus) or between two different parts of the same filament (as 

 in Saprolegnia) . In each instance the fertilized egg forms a zygote 

 (zygospore) which develops a new hypha. 



Examples: Rhizopus (black bread mold) (Fig. 36) and Saprolegnia 

 (water mold) (Fig. 64). 



(2) Class Ascomycetes. — The ascus (sac) fungi belong to the 

 class Ascomycetes (as ko mai -se' tez) (Gr. ascus, sac; mycetes, fungi) 

 because at some stage in their life cycle all of them may reproduce by 



