showing- also the manner in which the cortex-tubes interdentate 

 (from above and from below). " r," the apical cell of each cortex 

 system; " n," the nodes; "in, "the internodal cells; "1," the lateral 

 cells. 



Fig. 22 represents the fully developed cortex of Ch. fragilis. It is, 

 however, rare that we find a perfectly regular system in Ch. fragilis ; 

 this is more generally seen in Ch. sejuncta and the various sub- 

 species of Ch. gymnopus. In Ch. fragilis great variability is ob- 

 served, generally in the way of a redundancy of cortical cells in any 



n. 



w. 



x- 



T 



fl. 



n. 



Fig. 21. 



Fig. 22. Fig. 23. 



given section, due to the overlapping of the lateral tubes. Fig. 23 

 (drawn from nature) illustrates this peculiarity. " 1' " is a lateral cell 

 which, normally, should have stopped at ' ' x, " as shown by the 

 dotted line, but which grew on and pushed in between the other 

 laterals; a section just above "x" would show an extra cell. 



The normal mode of union of the lateral cells is by horizontal 

 (blunt) ends, as at "a," "a, "while the oblique overlapping of these 

 ends, as at "b," "b," is, like the characteristic cortex of our dioecious 

 Ch. aspera. In this species the cortex is only sub- triple-corticated, 

 the variation being toward a suppression of the lateral cells. 



