190 



R. K. 'BENSLEV. 



leave a peripheral zone of cytoplasm wholly free from the canals 

 which constitute it. In Fig. 2 are shown four of the large wedge- 

 shaped cells from the region of most active division of the der- 

 matogen. in which the type of the canalicular system is well 

 brought out. Here it will be seen that in these plant cells, as 

 in the animal cells, the network tends to be concentrated on one 

 side of the nucleus, and, as in the epithelial cells, this point of 

 concentration is not one of the division poles of the nucleus but 



FIG. 2. Four cells of outer layer of root tip of onion, showing more advanced 

 condition of the cytoplasmic canals. X 800. 



corresponds to one side of the equator of the future spindle. 

 The system constitutes a closed system of canals, lying in very 

 close relation to the nucleus, never, however, invading, in dividing 

 cells, the spindle territory. From this network run out branches 

 which end freely often near the cell wall in a small expansion. 

 Many of the canals in some preparations, and this is particularly 

 true of the smallest canals, such as those shown in Fig. I, show 

 moniliform enlargements, as if they were on the point of breaking 

 up into a row of vacuoles, or possibly, as if they had just been 

 formed by the coalescence of a row of vacuoles. Again fre- 

 quently, the canals show a spiral or tortuous course, as if they 

 were fixed while in a condition of internal tension, which re- 

 sembles very closely the spiral or tortuous condition found in many 

 nerve cells (etat spiremateux of Nelis). 



Tracing this system in the older and older cells of the root tip 

 it is found that as the cell retreats from the growing point, the 

 canals become progressively larger and larger. In the inter- 

 mediate stages of this process the condition depicted in Fig. 3 

 is obtained. Here there is still a continuous system of ran.il- 

 but they are fewer in number and broader than in the younger 



