THE FORMATION OF HYPHAL FUSIONS 



3i 



opposing points and simultaneously they send out hyphal pegs, as 

 shown at B. At C and D the pegs are shown growing toward one 

 another ; at E the pegs have come into contact at their apices ; 

 and, finally, at F the pegs have already fused at their apices and 

 have formed a compound bridging hypha. In Fig. 16 a series of 



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FiG. 15. — Diagram showing successive stages in a peg-to-peg fusion in one of the 

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

 mycetes). A, two older hyphae, a and b, which happen to be more or less 

 parallel to one another, are now stimulating one another morphogenically 

 where they have approached nearest to one another. B, as a result of this 

 mutual stimulation, the two older hyphae have sent out opposing pegs. C, the 

 pegs are growing in length. D, the ends of the two pegs are stimulating one 

 another tropically, in consequence of which they are growing toward one 

 another. E, the ends of the two pegs have met. F, the pegs have fused with 

 one another and have thus formed a bridging hypha between the two older 

 hyphae a and b. Time which elapses between stage A and stage F varies with 

 the rate of growth of the pegs, but is often of the order of 30-40 minutes. 



similar stages in a peg-to-peg fusion is shown, with the difference 

 that the older hyphae are very much nearer together than those 

 illustrated in Fig. 15. 



The two older hyphae which give rise to a pair of pegs often run 

 more or less parallel to one another (Figs. 15 and 16). but they may 

 cross one another at any angle up to a right angle. When they 

 cross one another, the two pegs are produced at the crossing, i.e. 

 at those points in the two hyphae which are nearest to one another 



