ASCOMYCETES—EUASCI— ASPERGILLUS 



267 



Fig. 89a. Aspergillus nidulans. 1. 

 Conidiophore. 2. Branch of mycelium 

 with asci and ascospores, magnified. 2. 

 Asci. 3. Cross section. Ascus. All 

 greatly magnified. (After Eidam.). 



prolonged to form a short tube or beak; numerous transparent asci arise from 

 the base of the perithecium, these contain the ascospores; between the asci 

 slender filiform bodies, called the paraphyses. Polymorphic fungi with conidia, 

 spermogonia, and pycnidia, supposed to be connected with the ascigerous stage. 

 The formation of the ascospores is in some cases presented by the development 

 of sexual organs in which genuine fertilization occurs. The reproduction can 

 be illustrated by the manner in which it occurs in the powdery mildew of the 

 lilac, Microsphaera Alni. 



The mycelium spreads over the surface of the lilac leaf; the fungus draws 

 its nourishment from its host by means of haustoria which penetrate the epi- 

 dermal cells; the mycelium produces erect branches which bear these spores 

 in a moniliform chain, the end spore being the oldest; these summer spores 

 germinate immediately and propagate the fungus ; later two hyphae cross and 

 there arises an oval cell, the oogonium, which is separated from the hypha by 

 a cell-wall at the base; from the same hypha springs a longer and thinner cell, 

 also cut off by a cell-wall ; this cell is above the oogonium, and is known as the 

 antheridium ; from the base of the oogonium other cells arise which soon enclose 

 it; finally a brown perithecium is formed which bears dichotomously branched 

 appendages; the perithecium contains the asci, in which are found the asco- 

 spores, which germinate, probably, in the spring. The accompanying figure 

 after Harper illustrates the development. 



Another type of one of the Sphaeriaceae, the Gibbellina cerealis, is common 

 on stems of wheat where it produces at first a grayish brown circular spot, the 

 mycelium frequently encircling the stem. The conidia are oval, the perithecia 

 are immersed. 



