44 PHYCOMYCETEAE 



reproduction by oogones with usually one egg and periplasm, fertilized by an 

 antherid through a conjugation tube. Order Peronosporales (Chap. 6) 



Key to the Orders of Nonflagellate Phycomyceteae 



Walls of the mycelium readily responding to the test for cellulose by chloriodide 

 of zinc. 



Parasites entirely within the tissues of the aerial parts of higher plants and 

 forming on their branched, occasionally septate, coenocytic hyphae large, 

 thick-walled intercalary or terminal resting spores within which, upon ger- 

 mination, are produced numerous small spores which upon escaping may 

 unite by twos and then infect other host plants. Relationship very doubtful. 



Order Protomycetales (Chap. 6) 



Parasites in the alimentary canals of Arthropoda, forming slender, at first non- 

 septate, coenocytic hyphae which very rarely branch. The contents of the 

 hyphae are transformed by formation of septa into endospores which escape 

 through basal or apical openings. Larger endospores may be formed in which 

 by a sexual (?) process there is a union of nuclei. Relationship very doubtful. 



Order Eccrinales (Chap. 7) 

 Walls of the mycelium not readily responding to tests for cellulose. Chitin-like 

 substances present. 



Saprophytes or more rarely parasites (mainly in fungi). Mycelium relatively 

 large and abundant, more often nonseptate, at least when young. Asexual 

 reproduction by aplanospores produced in sporangia or the latter reduced 

 to conidium-like sporangioles. Sexual reproduction by the union of unequal 

 or almost equal gametangia to form "zygospores." 



Order Mucorales (Chap. 7) 



Parasites in insects or in desmids or fern-prothallia or fungi or saprophytes on 

 dung of lizards and frogs. Mycelium at first coenocytic but early becoming 

 septate and very often breaking up into short "hyphal bodies." Asexual 

 reproduction mostly by formation on external conidiophores of terminal 

 conidia which are shot off with violence. Sexual reproduction by union of 

 apparently equal gametangia to form thick-walled zygospores. 



Order Entomophthorales (Chap. 7) 



Parasites in soil-inhabiting amoebae and nematodes or in the alimentary canal 

 of aquatic insects. Mycelium (except where thickened haustoria are pro- 

 duced) slender, at first coenocytic. Asexual reproduction by the formation 

 of terminal, ellipsoidal or fusiform conidia, single or in chains, or of similar 

 lateral conidia. Sexual reproduction by the union of apparently equal game- 

 tangia, adjacent in the same hypha or in separate hyphae lying in close 

 proximity, or at the ends of long, slender filaments. 



Order Zoopagales (Chap. 7) 



Order Chytridiales. The Chytridiales are comparatively simple in 

 their structure and for that reason are considered first. Whether this 

 simplicity is due to their primitive nature or whether it is due to simplifi- 

 cation from more complex forms is a matter of dispute and will be dis- 

 cussed at more length in Chapter 17 on the Phylogeny of the Fungi. 



This order includes a number of families of fungi that are either largely 

 aquatic or depend upon the presence of water for their dispersal. They 

 are either parasitic in the roots, stems, or leaves of higher plants; in algae; 



I 



