CHAPTER III 

 FRUCTIFICATIONS 



In most fungi, at a definite age and under favorable conditions of 

 nourishment, the mycelium proceeds to the formation of fructifications. 

 In the simplest unicellular families, as in the protozoa, the whole (unicellu- 

 lar) thallus becomes transformed into a fructification. These forms are 

 called holocarpic. The thallus (vegetative condition) and the fructifi- 

 cation (reproductive condition) of the same individual show in some cases 

 two successive phases of development; in other 

 cases these phases are concealed and are only recog- 

 nizable as different because of their functions. 



In the other fungi, the thallus and fructification 

 are separate from each other both in time and space ; 

 only a portion of the thallus is used for the forma- 

 tion of the fructification, while the rest remains to 

 serve its original vegetative function. These forms 

 are called eucarpic. 



The products of the reproductive processes are 

 chiefly spores. Spores are characteristically formed 

 cells or groups of cells which separate from the 

 mother plant and may grow independently to new 

 individuals. They serve either for propagation 

 (multiplication and dispersal) or overwintering (as 

 hypnospores or resting spores). 



In the simplest case, they arise by the separation 

 of hyphal cells (Fig. 263, 1), which grow into new 

 hyphae. These individual cells are called oidia and fig. 4. — Saprolegnia 

 are homologous to the cells of a sprout hypha, only «**»• . Zoosporangium 



& r ill discharging zoospores, o. 



the latter arise by sprouting rather than by the (After Kiebs.) 

 breaking up of a hypha. 



From oidia, there is an imperceptible transition to definite spores, 

 characteristic in form, color or sculpturing of the wall. In many cases 

 they are cut off directly from the ordinary hyphae; in other cases they 

 arise on special sporophores. If these sporophores form the spores endo- 

 genously from particular sporogenous cells, sporangia, they are called 

 sporangiophores, and the spores, if they are naked and motile, are called 

 zoospores (Fig. 4), or, if they are enclosed and non-motile, sporangio- 

 spores (Fig. 5, sp). If the sporophores cut off their spores exogenously, 



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