54 



RESEARCHES ON FUNGI 



by the older hypha r. At first all three pegs grew straight forward. 

 Then both of the pair of pegs d and e bent toward the single peg c. 

 However, the peg c bent toward e as if d were not in existence. 

 Finally, as shown in B, c fused with e and then d ceased to grow. 

 Probably e stimulated c slightly more than did d and thus won the 

 competition by superior attractive power. Why an older hypha 



should produce two 

 pegs right and left of an 

 opposing peg instead 

 of one opposite peg is 

 at present a mystery. 



After one has stud- 

 ied all the types of 

 fusions in actual for- 

 mation, it is not diffi- 

 cult to interpret the 

 nature of the fusions 

 that one finds already 

 in existence in an older 

 mycelium. Thus in 

 Fig. 24 we can in- 

 terpret some of the 

 fusions there seen as 

 follows : those at o 

 and w, hypha- to-hypha 

 fusions ; those at p, 

 q, m, and x, hypha- to- 

 peg fusions ; and those at n and v, peg-to-peg fusions. 



A photomicrograph showing several very short bridging hyphae 

 uniting long hyphae which have crossed one another more or less 

 at right angles is reproduced in Fig. 28. These bridging hyphae, 

 doubtless, were formed by peg-to-peg fusions. As they are directed 

 more or less perpendicularly to the plane in which the long hyphae 

 lie, they are seen in end view and therefore appear as dark disc- 

 shaped structures. They were formed not immediately after the 

 long hyphae crossed one another but much later when the culture 

 medium was becoming exhausted. It is under such conditions that 



Fig 



28. — Pleuruye curvicolUi. Photomicrograph 

 of a mycelium produced from spores sown in 

 a hanging drop of cleared dung-agar on the 

 previous day. To show the very short peg- 

 to-peg fusions which have been formed where 

 two older hyphae have crossed one another 

 more or less at right angles. The bridging 

 hyphae are perpendicular to the plane of the 

 photograph and hence appear as dark circles. 

 Magnification, COO. 



