3o6 



FUNGI 



only, Bacteria are as little related in structure and development as bats 

 are to birds ; the relationship is even less, because there are a few, 

 though only a few, true Bacteria which contain chlorophyll and decom- 

 pose carbon dioxide, and which are therefore not Fungi in the physio- 

 logical sense.' 



Histological Characteristics. 



The thallus of fungi consists of one or more cylindrical hypha 

 branching in monopodial fashion, rarely dichotomously, and increasing 

 by apical growth. In numerous instances the hypha remains, for a 

 period at least, unsegmented, but most frequently transverse septa are 

 formed either in the apical cell or in segment-cells of the first order, 

 The thallus of the simple filamentous fungi consists of one hypha with 

 its ramifications. The so-called compound thallus of larger fungi is 

 formed of h)'phse of which the branches meet and remain in close 

 contact. While all fungi have the filamentous habit to begin with, 



Fig. 266.— Clamp-connec- 

 tions ; mycele of H\~ 

 pochiiu^ centrifugus Tul. 

 (x 390). (-\fterde Bary.) 



Fig. 2^7. — Pseudo-parenchyme breaking up at end 

 into leparite hyphae : Nectria cinnabarina Fr. 

 (highly magnified). (After Reinke ) 



some remain so throughout their whole development, and others are 

 characterised by both habits in different periods of their life-history. 

 It should also be mentioned that the whole thallus of a fungus may be 

 reduced to a single globular cell. Clamp-connedions take place, especi- 

 ally in the Basidiomycetes, between adjoining segment-cells of the same 

 hypha by means of a protuberance emitted from the one nearer the 

 growing-point. This protuberance issues immediately above the trans- 

 verse wall, and effects a junction with the cell beneath. By this means 

 open communication is maintained between the cells for a time, but it is 



