THE TRANSLOCATION OF PROTOPLASM 153 



in one direction only, without any more or less rhythmic reversals 

 in direction ; (2) by the absence of peripheral currents of protoplasm 

 flowing in a direction opposite to that of the main stream ; and 

 (3) by the fact that the flow of protoplasm often takes place through 

 a cell for long periods of time without the vacuoles being involved 

 in the movement. 



In the Higher Fungi, the vacuoles appear to be strongly attached 

 to the immovable outermost non-granular layer of protoplasm 

 lining the cell-wall ; whereas, in the Mucorineae, the vacuoles 

 appear to be not so attached or not attached so strongly. Hence 

 perhaps it is that, in the Higher Fungi, the vacuoles are only torn 

 loose and carried off by the streaming protoplasm when the current is 

 very strong ; whereas, in the Mucorineae, the vacuoles are trans- 

 located by the streaming protoplasm even when the current is very 

 weak. 



In the Mucorineae, the streaming takes place in a non-septate 

 mycelium, so that the flow of the protoplasm from the mycelium 

 into the young sporangia is not hindered by any cross-walls. The 

 absence of septa facilitates the flow of protoplasm to the growing 

 points and may be correlated with the rapid growth in length of the 

 vegetative hyphae and of the sporangiophores. Septa are eventu- 

 ally formed : (1) across the base of lateral hyphae, etc., which have 

 evacuated their main mass of protoplasm and are about to die 

 (Fig. 76) ; and (2) across the base of sporangia after these have 

 swollen up and have been filled with protoplasm (Fig. 77). Thus, 

 in the Mucorineae. septa are formed only after the flow of protoplasm 

 out of or into an organ has finally ceased. 



Fig. 77.- — Rhizopus nigricans. The translocation of protoplasm from a mycelium 

 into a sporangiophore, the accumulation of protoplasm in the sporangium, and 

 the subsequent walling-off of the sporangium by the wall of the columella. 

 The mycelium developed in a hanging drop of gelatine ; the sporangiophore 

 was parallel to the hanging drop and finally touched its surface. A : the 

 hyphae a and b, now dead, and the hypha c, still living, have evacuated their 

 massive labile protoplasm into, and have been walled-of! by septa from, the 

 hypha d. The hypha d has grown out into the sporangiophore e which, in turn, 

 has become swollen at its apex so as to form a sporangium. A vacuole v has 

 been formed in the cell d and is growing in size. B, several hours after A : the 

 hypha d and the lower part of the sporangiophore have now become highly 

 vacuolated and protoplasm has accumulated (become denser) in the sporangium. 

 C, about five hours after B : the dense protoplasm in the sporangium has now- 

 become cut off from the much less dense protoplasm of the sporangiophore by 

 a columella- wall. Drawn by A. H. R. Buller and C. C. Neufeld. Magnification, 



J 1 Oj. 



