MOLDS 37 



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 

 hjrphse 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 corddiophores, 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 cMamydo- 

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

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

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

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

 materials. These sclerotia are frequently distinctive of the species 

 producing them by size and appearance. They sometimes resemble 

 the sexual fruiting masses. Resting structures of either type, es- 

 pecially when large, commonly produce tj^ical spore-bearing structures 

 at once after germinating. Many very complex fruit bodies such as 

 the mushrooms appear to be entirely asexual in origin. 



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 classifjang fungi, certain t3^es of 

 spore formation are found to be characteristic of particular groups. 

 Since within these groups various accessory tjrpes of fruiting occur, so 

 that some species show three or even more forms of spores, that type 

 of spore formation which is regarded as characteristic of the group is 

 known as the perfect stage. If sexual fruits are found, these constitute 

 the perfect stage of the group; if no such fruit is found, the most 

 characteristic asexual form is used, as for example the common mush- 

 room of commerce which is asexually produced so far as we know, yet 

 represents the most perfect and most constant fruiting form produced 



