32 



RESEARCHES ON FUNGI 



(Fig. 17). The length of the pegs depends on the distance apart of 

 the two older hyphae which produce them. This distance usually 

 does not exceed 25 [i. Peg-to-peg fusions are often produced when 



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Fig. 16. — Diagram showing successive stages in a peg-to-peg fusion in one of the 

 Higher Fungi ( Pyrenomycetes, Discomycetes, Hymenomycetes, and Gas- 

 tromycetes). In contrast with the diagram shown in Fig. 15, the two 

 older hyphae are here very close together. A, parts of two long almost 

 parallel older hyphae which lie very close together. B, a mutual morpho- 

 genic stimulation has resulted in the production of opposing pegs. C, 

 the pegs have met. D, the pegs have fused and have formed a very 

 short bridging hypfut connecting the two older hyphae. Time which 

 elapses hetween stage A and stage D is often of the order of 20 minutes. 



the two older hyphae are 7-15 \x apart and still more frequently 

 when the two older hyphae are only 3-5 [i apart. Even where two 

 older hyphae happen to touch one another when running more or 



Fig. 17. — Diagram showing the formation of very short bridging 

 hyphae, derived from peg-to-peg fusions, between older hyphae 

 which have crossed one another. A, four older hyphae with 

 three crossing places. B : the same, after the mycelium 

 has increased in age and the culture medium has become ex- 

 hausted ; at each of the crossing places, a very short bridging 

 hypha, seen in the axial view, has been formed. The con- 

 struction of each bridging hypha might be accomplished in 

 10 minutes. 



less parallel to or crossing one another, bridging hyphae may be 

 formed. Under such conditions the two pegs, at the moment they 

 begin to fuse with one another, are no more than convex processes 

 which have flattened out against one another. 



It sometimes happens that, where two older hyphae lie parallel 



