108 RESEARCHES ON FUNGI 



until another vacuole joins it and melts with it, thus increasing its 

 size (a-c) ; then the stream of protoplasm, instead of passing in 

 front of the vacuole as it did when the vacuole was smaller, may 

 press the vacuole against the septum (c) and so cause it to constrict 

 off pieces of itself through the pore of the septum (d and e). The 

 vacuole, after being thus diminished in size, may then round itself 

 off, so that the protoplasm flows in front of it through the pore, and 

 it may thus remain until it is joined by one or more other vacuoles (/), 

 when, having again increased its volume, the stream of protoplasm 

 may once more press it against the septum and force pieces of it 

 through the pore. In the second case, a larger or smaller vacuole 

 may be pressed through a pore as a whole without being broken 

 into pieces. This often happens when the stream of protoplasm is 

 flowing very rapidly. The vacuole is carried to a septum (g and h), 

 is flattened out against the septum (h), and is then forced through 

 the pore (i-k) without being broken up. Whilst passing through 

 a pore, the vacuole is much constricted ; but, as soon as the passage 

 has been effected, it rounds itself off and resumes its original shape. 

 A large vacuole, such as that shown in Fig. 60 at F, when being 

 carried along by a dense stream of protoplasm, is usually much less 

 convex behind than in front, thus assuming a form like that of the 

 moving vacuoles of the Mucorineae. 1 



It sometimes happens that a vacuole, as it is passing through 

 a septum under pressure from a rapid stream of protoplasm, instead 

 of passing through the pore intact, breaks up in the course of its 

 passage into two or more pieces. 



The protoplasmic stream passing along a hypha is often a steady 

 one ; but in some hyphae in which the flow was very rapid it was 

 seen to be somewhat pulsatory, in that it exhibited little jerks 

 forward, the jerks being irregular, on the average about one per 

 second. The unevenness of the flow appeared to be caused by large 

 vacuoles being caught momentarily in front of septa or at sharp 

 bends in the hyphae. 



Rate of Flow of the Protoplasm. — The rapidity of flow of the 

 protoplasmic stream in the mycelium of Fimetaria fimicola at about 

 20° C. was estimated by observing the rate of movement of 



1 Cf. Figs. 44 and 46, pp. 77 and 70. 



