MOLDS 37 



masses, which may be fleshy, woody, carbonaceous, leathery and 

 even horn-like in texture, as seen especially in the mushrooms, bracket- 

 fungi, etc., but even in such cases the early stages show the structures 

 to originate from masses of fungous threads. 



The formation of differentiated reproductive cells is, in general, 

 characteristic of the fungi. The method of reproduction presents great 

 variety. In the simplest forms, the reproductive cells are scarcely, if 

 at all, distinguishable from the vegetative cells. In some species whole 

 hyphae break up so that each cell forms the starting-point of a new 

 colony. Other forms develop special branches bearing reproductive 

 cells. From these it is but a step to the production of fruiting branches, 

 characteristic in form, called conidiophores, bearing cells markedly 

 specialized as reproductive by form and frequently also by color, 

 called conidia. These conidia are entirely asexual in origin and capable 

 of growing directly into new colonies, although in many cases they are 

 provided with resistant walls which enable them to live for long periods 

 if conditions are unfavorable to growth at once. In other species, 

 specialized resting cells with resistant walls are formed to enable the 

 plant to survive unfavorable conditions. These are called chlamydo- 

 spores or sometimes cysts. The name gemma is sometimes applied to 

 similar structures, preferably to such as grow at once. The same end is 

 reached in still other groups by the formation of sclerotia which are 

 hard masses or balls of thick-walled cells filled with concentrated food 

 materials. These sclerotia are frequently distinctive of the species 

 producing them by size and appearance. They vary from microscopic 

 in size to masses weighing many pounds and may perhaps in cases be 

 aborted fruits. They sometimes resemble such sexual fruiting bodies. 

 Resting structures of either type, especially when large, commonly 

 produce typical spore-bearing structures at once after germinating. 

 Sexuality among the fungi has been difficult to demonstrate in some 

 groups with complex fruit bodies. It is certainly suppressed, if not 

 entirely wanting, in whole series of cosmopolitan forms and present 

 only in rare species in other groups. 



The systems of classification used are largely based upon the types of 

 sexual fruit bodies produced. Where such fruit bodies are not known, 

 the method of formation of the asexual spores furnishes the most 

 satisfactory basis for grouping. In classifying fungi, certain types of 

 spore formation are found to be characteristic of particular groups. 



