CHAPTER XI 



MOULD FUNGI 



SUBCLASS PHYCOMYCETES 



The fungi of this subclass are distinguished by their siphon-like 

 hyphge, because these hyphae are unicellular and multinucleate and sug- 

 gest the algae of the family Siphonace^ to which Vaucheria belongs. 

 Hence the fungi of the subclass PHYCOMYCETES {4>vkos, seaweed + 

 livKTis, a fungus) are usually designated as algal fungi. Although the 

 absence of transverse septa in the hyphae is used as a fundamental char- 

 acteristic, yet in the formation of the reproductive organs transverse 

 walls or septa cut these organs off from the rest of the vegetative 

 mycelium. Transverse septa are found regularly in some of the genera, 

 such as Dimargaris, Dispira, Protomyces and Mucor, so that the general 

 statement above is modified by such exceptions. A fungus, Leptomitus 

 lacteus, found in ditches and rivers shows a characteristic segmentation 

 of the hyphae, where through the deposit of a substance known as cellu- 

 lin the lumen of the hyphae is nearly closed, but at the point of constric- 

 tion, a small pore remains through which the protoplasm passes.^ 



There are genera of the family Chytridiace^, such as Reessia and 

 Rozella in which the protoplasm during the vegetative state is not sur- 

 rounded by a cell wall, but is naked, and amoeboid in the host cells. 

 The fungi of this subclass are saprophytic or parasitic, aquatic, or 

 aerial, living endophytically as a rule. A few are parasitic on insects 

 and fishes. Two orders are distinguished, viz., the ZYGOMYCET- 

 ALES and the OOMYCETALES. 



ORDER ZYGOMYCETALES 



The fungi of this order show a strongly developed mycelium con- 

 sisting usually of unicellular, sometimes pluricellular, multinucleate 

 hyphas. These hyphae are distinguished in the typic forms as the rhiz- 

 oidal hyphae, aerial hyphae and reproductive hyphae. Vegetative re- 



1 Massee, George: Text-book of Fungi, 1906: 242. 

 92 



