THE FORMATION OF HYPHAL FUSIONS 37 



the stages in the formation of two particular clamp-connexions were 

 passed through in 40 and 45 minutes respectively. In both C. ster- 

 quilinus and C. lagopus, the hook-septum is always formed a minute 

 or two after the septum across the main hypha (Fig. 19, A, cf. stages 

 nos. 4, 5, and 6). 



The Function of a Clamp-connexion.— The existence of clamp- 



Fk;. 19. — Coprinus sterquilinus. A, semi-diagrammatic representation of nine 

 stages in the formation of a clamp-connexion on the side of a terminal cell of 

 a hypha : no. 1, the middle part of the cell, the arrow indicates direction of 

 growth : no. 2, a hook is growing outwards ; no. 3, the hook has grown back- 

 wards and is now growing inwards ; no. 4, the apex of the hook has touched 

 the side of the main hypha ; no. 5, a septum (with a central pore, characteristic 

 of mycelial septa in general) has been formed across the main hypha ; no. C, 

 a septum has been formed across the base of the hook, thus converting the hook 

 into a clamp-cell : no. 7, a peg is growing outwards from the main hypha 

 opposite the end of the hook ; no. 8, the end of the hook and the end of the peg 

 have flattened out against one another; and no. 9, the double wall between 

 the hook and the peg has now broken down, the clamp-cell has thus fused with 

 the penultimate cell, and the clamp-cell as such no longer has an individual 

 existence. In a hanging drop of cleared dung-agar at room temperatures, all 

 the stages in the formation of two clamp-connexions were passed through in 

 40 and 45 minutes respectively. B, C, and D, camera-lucid a drawings of par- 

 ticular clamp-connexions ; B and C, seen from the side ; D, seen fro.n above. 

 The arrows indicate the direction of growth of the hyphae. On the left of each 

 of the three clamp-connexions can be seen the part contributed by the peg. 

 In B and C, the penultimate cell is sending out a lateral hypha. Magnification : 

 A and C, 920 ; B and D, 860. 



connexions in the diploid mycelium of the Hymenomycetes from 

 the Thelephoraceae to the Polyporaceae, and in the Gastromycetes J 



1 Among Gastromycetes which develop clamp-connexions is Sphaerobolus 

 stellalus. If one places a gleba in a hanging-drop of water, there soon grows out 

 from it a diploid mycelium bearing clamp-connexions (vide infra). 



In her recent Monograph " A Study of the Genus Podaxis " (Mycologia, Vol. XXV, 

 1933, pp. 1-33), Miss E. E. Morse has expressed the view that this genus, with its 

 " unorganised hymenia," " may have arisen, via Leucogaster and Alpova, from the 

 Ascomycetes." In material of Podaxis pistillaris, kindly sent to me by Miss Morse, 



