44 



RESEARCHES ON FUNGI 



general. I myself have observed the backward growth of the hook 

 in various Coprini, including C. sterquilinus and C. lagopus ; and, 

 from the disposition of the septa at the clamp connexions, I have 

 made the deduction that backward growth of the hook occurs in 

 Omphalia fiavida, Polyporus squamosus, and Sphaerobolus stellatus. 



In view of the fact that on leading hyphae of the mycelium of 

 Coprinus lagopus, other Hymenomycetes, and Gastromycetes the 

 ordinary vegetative lateral hyphae grow forward, so as to make an 

 acute angle * with the parent hypha, it is of interest to ask the 

 question : what biological advantage, if any, accrues to a mycelium 

 by reason of the fact that a clamp-connexion hook, which originates 

 as a lateral hypha, grows backwards instead of forwards ? 



For some years the problem of the backward growth of the hook 

 of clamp-connexions puzzled me. At length, in November, 1932. 

 I suddenly thought of a reasonable solution based on certain 

 experimental data having to do with the relation of nuclei and 

 cytoplasm. 



In Coprinus lagopus (= C. fimelarius of Mile Bensaude) Mile 

 Bensaude 2 found that the formation of a clamp-connexion is 

 associated with a conjugate nuclear division, and in a diagrammatic 

 illustration, reproduced here in Fig. 2 1 , she represented five successive 

 stages in the whole process. In the fourth stage (Fig. 21), one of 

 the nuclei is imprisoned temporarily in the clamp-cell ; while, in 

 the fifth stage, fusion has just been completed and the imprisoned 

 nucleus is escaping and joining its yoke-companion. 



Mile Bensaude's fourth stage of clamp-connexion development 

 I have represented diagrammatically in Fig. 22 at A. Here are 

 shown three complete cells : (1) the ultimate cell which at its apex 

 is growing rapidly in length, (2) the penultimate cell which has ceased 

 to grow in length, and (3) the damp-cell destined soon to fuse with 

 the penultimate cell of the parent hypha. While in Fig. 22 at A 



1 In Coprinus lagopus this angle is W-U>°. Vide these Researches, Vol. IV. 1931 . 

 p. 199 and Fig. 118, p. 202. 



2 Mathilde Bensaude, Becherches stir h cycle evolutif et la sexualite chez les 

 Basidiomi/cetes, Nemours, 1918, pp. 1-156. 



3 In mycelia, as Reinhardt showed forty years ago (" Das Wachsthum der 

 Pilzhyphen," Jahrb. f. wiss. Bot., Bd. XXIII, 1892), the hyphae elongate at their 

 extreme tips only. Intercalary growth in length of mycelial hyphae is unknown. 



3 



