THE TRANSLOCATION OF PROTOPLASM 161 



The advantage in each septum of a Higher Fungus being provided 

 with a small pore seems to lie in this : that ( 1 ) the pore permits of 

 protoplasm passing readily out of one cell into the next and thus 

 being moved to places where it is needed, as may actually be seen 

 where the protoplasm is very granular and streaming is rapid ; 

 while, (2) the pore can be closed instantaneously when one of the 

 cells adjacent to it is killed or dies (cf. Fig. 68, p. 132). The septum 

 in the Higher Fungi is therefore constructed in such a way that it 

 interferes but little with the passage of materials from one cell to 

 the other so long as the cells on each side of it are living normally, 

 and yet in such a way that it can have its pore blocked the moment 

 one of the cells adjacent to it is killed or dies, the escape of living 

 protoplasm through a pore being thus rendered impossible. 



A septum serves not only to protect the protoplasm of one cell 

 against the deleterious effects of the death of the protoplasm in an 

 adjoining cell, but it also plays an important part in initiating the 

 process (already described) by which the living parts of a mycelium 



Fig. 80. — Rhizopus nigricans. The reaction of a hypha to a mechanical wound : 

 the plugging of the end of a broken hypha with coagulated protoplasm and 

 the subsequent formation of a septum by the living protoplasm near the dead 

 protoplasm. A : a portion of a three-days-old mycelium grown in nutrient 

 gelatine in a van-Tieghem cell, represented as if seen in a median-longitudinal 

 section ; the hypha was cut across at a by pressing upon it with a sharp scalpel ; 

 immediately some of the protoplasm escaped from the hypha and collected at 

 the hypha's mouth so as to form the ball b ; the ball of protoplasm and the 

 adjoining protoplasm c in the hypha coagulated and died ; at d the living 

 protoplasm e is in direct contact with the coagulated protoplasm c ; the septum 

 s divides a lateral part of the mycelium which has already evacuated its massive 

 protoplasm from the main unexhausted hypha here shown. B, about 10 minutes 

 after A ; C, 10 minutes after B ; and D, 10 minutes after C : protoplasm in 

 the wounded hypha has continued to die, so that the junction between the 

 coagulated and the living protoplasm has passed down the hypha successively 

 from d to /, / to g, and g to h ; after the protoplasm had died down to h, further 

 coagulation of the protoplasm ceased as may be seen by comparing D with 

 E-J. E, 40 minutes after D: the living part of the hypha has begun to evacuate 

 its massive mobile protoplasm as is shown by the growth of the two large 

 vacuoles. F, 10 minutes after E : the vacuoles have increased in number and 

 in size. G, 20 minutes after F : the vacuoles are still increasing in size. 

 H-J : the formation of a septum across the living part of the hypha a short 

 distance from the dead part. H, 95 minutes after G : a circular ridge of 

 protoplasm has appeared at i. I, 30 minutes after H : in the ridge of proto- 

 plasm a septum is developing as an annular ingrowth from the lateral wall. 

 J, 26 minutes after I : the septum has now become complete and it divides a 

 smaller living cell k from a larger living cell I ; the living protoplasm in A; is 

 bounded at one end by the plug of dead coagulated protoplasm,;' and at the other 

 end by the newly-formed septum ; the cell I has evacuated most of its massive 

 labile protoplasm, presumably by vacuolar pressure. Drawn by A. H. R. 

 Buller and C. C. Neufeld. Magnification, 706. 

 vol. v. M 



