34 RESEARCHES ON FUNGI 



of Hymenomycetes, e.g. Coprinus curtus and Psalliota campestris, 

 which must be considered as exceptional, they are absent. Their 

 formation has been described by Brefeld, Mile Bensaude, Kniep, 

 and others. Stages in the formation of a clamp-connexion in associa- 

 tion with conjugate nuclear division in a diploid mycelium of 

 Coprinus fimetarius (= C. lagopus of these volumes), as represented 

 by Mile Bensaude, are shown in Fig. 21 (p. 45). The final stage in 

 the development of a clamp-connexion involves the formation of an 

 anastomosis, and it is the mode in which this is accomplished that 

 is of interest to us here. A clamp-connexion in a Coprinus, Hypho- 

 loma, Collybia, etc., is formed in the terminal cell of a growing 

 hypha. From the middle of the cell a hook grows outwards, back- 

 wards, and then inwards toward the parent hypha ; two cross- walls 

 are formed, one across the base of the hook and the other across the 

 parent hypha ; and then the end of the hook fuses with the parent 

 hypha, there being thus left a little air-space between the loop and 

 the main hypha at the level of the septum which crosses the parent 

 hypha. 



Investigations on the details of clamp-connexion formation in 

 two species of Coprinus have taught me that the hook of a clamp- 

 connexion does not fuse directly with the main hypha as hitherto 

 has been supposed, but with a little blunt process or peg sent out by 

 the main hypha in response to a stimulus given by the apex of the 

 hook. 



Diploid mycelia of Coprinus sterquilinus and of C. lagopus were 

 grown in hanging drops of cleared dung-agar, and the process of 

 clamp-connexion formation was observed with the high power of 

 the microscope. In C. lagopus, the clamp-connexions are small, 

 but along each leading hypha they are produced at very regular 

 distances apart 1 and at the rate of about one every fifty minutes. 2 

 In C. sterquilinus, on the other hand, the clamp-connexions are much 

 larger ; but they are not formed at every septum nor by every 

 hypha 3 and, even on the leading hyphae, they are somewhat 

 irregular in their distribution, are produced at longer intervals of 

 time, and develop more slowly. 4 



1 These Researches, Vol. IV, Fig. 118, p. 202. 2 Ibid., p. 243. 



3 Ibid., Fig. 89, p. 159. 4 Ibid., Fig. 89, p. 159. 



