CHAPTER XV. 



MOULD-FUNGI I HYPHOMYCETES OR MYCELIAL FUNGI. 



OF this class of fungi only those are of special interest to the 

 pathologist which in some way or other are connected with 

 disease. The fungi consist of branched and septate threads 

 or hyphae ; each filament or hypha is composed of a row of 

 cylindrical cells, consisting of a membrane and clear proto- 

 plasm, the individual cells being separated from one another 

 by a thin transverse septum ; they increase in number by 

 fission, and in this way the filaments increase in length. The 

 growing ends of the hyphse are filled, not with transparent, 

 but with highly -refractive protoplasm. Some cells, by budding 

 out laterally, produce cylindrical threads, which subdivide into 

 a series of cylindrical cells, these by division and lengthening 

 forming a new branch-hypha. The filaments form by their 

 branches an interlacing feltwork, called thallus or mycelium. 

 The mycelial fungi which interest us, belong to the order 

 known to botanists as the Ascomycetes, They are characterised 

 by the fact that one or other branch of the mycelial-hyphce 

 produces at its end a series of spherical or oval cells the 

 conidia-spores or conidia. In addition to this some of the 

 hyphoe form peculiar large mother -cells, or sporangia, in the 

 interior of which spores are formed by endogenous formation. 

 When these sporangia are cylindrical or club-shaped, they 

 include eight spores, and are called asci ; the spores being 

 ascospores. All conidia or spores by germination grow into 

 the mycelial threads which become septate or subdivided into 

 a row of cylindrical cells ; these by division cause the 

 lengthening of the mycelial threads. 



(a) O'idium lactis. Here the mycelium is composed of sep- 

 tate branched filaments of various thicknesses. Some branches 



