FUNGI IMPERFECTi: THE IMPERFECT FUNGI 575 



forms makes their recognition as definite species difficult, even where the 

 perfect stages are not discovered. Furthermore the adaptation of the type 

 of spore or sporophore to special habitats may be responsible for similar- 

 ities among these that perhaps do not reflect real relationships. Thus the 

 fungi that live in wet habitats and frequently produce their spores on 

 hyphae that are completely submerged show many points of likeness; as 

 in the genera Varicosporium, Tetracladium, Heliscus, Lemonniera, Tri- 

 cladium, Tetrachaetum, Lunulospora, etc. The spores are usually slender 

 and with long branches which give them a great abihty to float. In some 

 genera these are aleuriospores, in the sense of Vuillemin (1910, 1911) and 

 in others are phialospores and radulaspores, in the sense of Mason (1933, 

 1937). To these Ingold (1942) would add the type "aquatic spore." A 

 phialospore is borne at the apex of a phialide, a "fusiform truncate, fusi- 

 form beaked or acuminate terminal portion of a hypha, from the apex of 

 which, or within which, thin-walled conidia are abstricted" (Mason). The 

 septum separating the spore from the phialide is not produced until the 

 spore is fully grown. An aleuriospore is a terminal portion of a hypha that 

 is early separated by a septum from the parent hypha. A radulaspore is 

 according to Mason a type "in which each spore is borne on a little 

 sterigma, without any reference to the growing-point of a hypha," as in 

 Botrytis cinerea. There is no direct evidence that these various aquatic 

 genera are closely related except in habitat. Ingold (1942, 1943, 1944) has 

 studied many of these and described several new genera. (Fig. 189.) 



As the life histories of various fungi are studied by pure culture 

 methods or by means of carefully controlled inoculations, from time to 

 time an imperfect fungus is connected up with its perfect stage. This may 

 perhaps be a species already known or may have been unknown there- 

 tofore. Klebahn (1918), the German mycologist, has made many such 

 connections. It often happens that the same species has several types of 

 asexual reproduction so that it may appear in several different form 

 genera. 



The many species and genera are usually divided into four form orders 

 as follows : 



Sphaeropsidales: conidia produced within pycnidia or niodifications of such 

 structures. A pycnidium is a perithecium-like structure and may be com- 

 plete, like the perithecium of the Sphaeriales and Hypocreales, or only the 

 top half may be present as in the perithecium-like spore fruit of the Hemi- 

 sphaeriales, or it may , open by a longitudinal slit as in the apothecia of 

 the Hysteriales or may be closed at first and finally open into a cup or 

 saucer-shaped structure, much like a miniature apothecium. 



Melanconiales: conidia produced singly or in chains, often surrounded by a 

 gummy mass, from conidiophores packed closely in a usually subepidermal 

 or subcortical layer, the acervulus. 



MoniHales: conidia formed on conidiophores which are separate, at least at 



