I54 RESEARCHES ON FUNGI 



In the Higher Fungi, on the other hand, the streaming takes 

 place in the mycelium after this has become divided up into cells 

 by septa. Each septum, as we have seen, has a small central pore 

 through which the moving protoplasm must pass. There can be 

 but little doubt that the septa do to some extent diminish the rate 

 of flow of the protoplasm from cell to cell although, as will be shown 

 in another Section of this Chapter, their presence in the mycelium 

 is fraught with important advantages. 



In the Higher Fungi, as Wahrlich discovered, 1 each septum 

 grows from the periphery of the hypha inwards but never becomes 

 complete ; so that, like a "closed " iris diaphragm of a microscope, 



Fig. 78. — Diagram to illustrate the formation of a septum in a hypha : 

 A-D, Ascomycetes and Basidiomycetes ; A-E, Phycomycetes as 

 represented by Rhizopus nigricans. A, a cross-section of a lateral wall of 

 a hypha at a place where a septum is to be formed. B-E, successive 

 stages in the formation of a septum by means of an annular ingrowth 

 from the lateral wall. The end-stage for the Ascomycetes and Basidio- 

 mycetes is shown at D, where the septum has a small central pore 

 through which protoplasm extends from cell to cell ; and the end-stage 

 for the Phycomycetes, as represented by Rhizopus nigricans, is shown at 

 E where the septum is complete. 



there is a small hole or pore left at its centre (Fig. 78, D). In the 

 Mucorineae, as the researches of Harper 2 and Swingle 3 have shown, 

 the wall of the columella is formed by the deposition of wall-substance 

 in a cleavage plane between two masses of protoplasm. 4 There was 

 the possibility that the septa formed across hyphae in the evacuating 



1 Vide supra, p. 95. 



2 R. A. Harper ; in respect to the formation of the columella in Pilobolus, vide 

 copies of his illustrations in the forthcoming Volume VI of this work. 



3 D. B. Swingle, " The Formation of Spores in the Sporangia of Rhizopus 

 nigricans and Phycomyces nitens," U. S. Dept. of Agric, Bureau: of Plant Industry, 

 Bull. XXXVII, 1903. 



4 It remains to be determined whether the wall of the columella is formed by an 

 even deposition of wall-substance throughout the cleavage plane or whether the 

 wall begins as an annular ingrowth from the lateral wall of the base of the sporan- 

 gium and then grows upwards in the cleavage plane to the apex of the columella. 



