INTRACELLULAR PROTOPLASMIC TRANSMISSION 039 



of Nemec's assertion that these protoplasmic structures represent special 

 paths of transmission analogous to the neuro-fibrillae of animal nerves. 

 Moreover, the author has since demonstrated that protoplasmic stream- 

 ing takes place within the fibrillar protoplasmic strands of the above- 

 mentioned large plerome elements, and that the longitudinally fibrillar 

 structure of these strands is due to the same morphological and physio- 

 logical conditions that produce the longitudinally fibrillar structure 

 previously described in connection with other forms of streaming 

 protoplasm. It appears, in fact, that streaming protoplasm in general 

 consists of elongated fibrous or lamellar plasmatic masses separated 

 from one another by long and exceedingly narrow vacuoles. 



If intracellular transmission of stimuli really depended upon the 

 presence of special protoplasmic fibrillae, these structures ought to be 

 present above all in those organs which are characterised by a high 

 rate of transmission ; they ought, therefore, to be readily observable in 

 the cells that are interpolated between such sense-organs as the tactile 

 pits or papillae of tendrils and irritable stamens, or the tactile hairs and 

 bristles of Cenfaurea, Aldrovandia and Dionaea on the one hand, and 

 the associated motor-tissues on the other. With regard to this point, 

 however, the author's investigations have invariably led to negative 

 results. 



Intracellular transmission must, therefore, either be a function of 

 the entire protoplast, or it must be principally located in the ectoplast. 

 The latter seems the more probable alternative, especially in view of 

 the fact that the protoplasmic connecting threads, which are held 

 responsible for intercellular transmission, are merely local extensions of 

 the ectoplast. It does not necessarily follow that the protoplasmic 

 strands which traverse the sap-cavity are never utilised for trans- 

 mission ; indeed, where the nucleus is suspended near the centre of the 

 cell, it is difficult to see how the impulses which it sends forth can 

 travel towards the periphery of the cell by any other means. It is 

 therefore quite possible that stimuli are actually propagated along the 

 fibrillar protoplasmic strands observed by Nemec in root-tips ; this 

 possibility does not, however, justify us in assuming that these fibrillar 

 strands are structures specially set apart for the work of transmission. 



The question finally arises, as to how far the velocity of trans- 

 mission depends upon the form of the cells in which transmission takes 

 place. If stimuli travel in the ectoplast, or indeed in any other part 

 of the peripheral cytoplasm, any elongation of the cells in the direction 

 of transmission will naturally reduce the distance to be traversed, and 

 hence increase the velocity of transmission ; for every decrease in the 

 number of transverse septa diminishes the loss of time caused by the 

 relatively slow transmission through the protoplasmic connecting 



