58 



RESEARCHES ON FUNGI 



mycelium grows very rapidly. Hanging drops of cleared dung-agar 

 inoculated with mycelium one day are ready for the study of hyphal 

 fusions on the next day. 



mm^^Fmm 



B 



^H^^aiis^ 



g^^^^j*^^^ 



Fig. 33.— Pyronema confluens. Four stages in the formation of a peg-to-peg fusion. 

 The branch-hypha o oame off from the hypha p at an angle of about 45° but, 

 with the help of a beading needle, it was brought parallel to p, as shown in 

 A-D. Within about four hours after o had taken up its new position, four 

 peg-to-peg fusions took place successively between o and p. The first two 

 fusions (to the left) are not shown. The third, shown in A, was formed by 

 the fusion of the two pegs a and b. The stages in the fourth peg-to-peg fusion 

 are shown in A-D. A : in the region of the letters o and p the hyphae o and p 

 are stimulating one another morphogenically. B, about 40 minutes after A ; 

 as a result of mutual stimulation, the hypha p has sent out the peg c and the 

 hypha o the two opposing pegs d and e ; d has already turned toward c, but c 

 is turning not toward d but to the nearer and shorter peg e. C, 21 minutes 

 after B ; the ends of the pegs c and e have grown toward one another and have 

 met. D, 8 minutes after C ; the pegs c and e have completely fused with one 

 another, thus forming the fourth bridging hypha between the hyphae o and p ; 

 the peg d, after the fusion was complete, ceased to elongate. The hyphae, 

 represented in optical section, are highly vacuolated and have centrally per- 

 forate septa. Magnification, 447. 



Hypha-to-hypha, hypha-to-peg, and peg-to-peg fusions are all 

 formed in the mycelium of Pyronema confluens and can readily be 

 found and identified as such in older cultures. 



