GROUPS OF TISSUES. OB TISSUE-SYSTEMS. 43 



to tell whether the tissues belong to them or to the sur- 

 rounding ground-tissues. The inner portion of the bundle 

 {9> y, t, t, Fig. 26, and s to t, Fig. 27) is made up of trache- 

 ary tissue of several varieties; on the inner edge of this 

 tracheary portion lie several spiral vessels (s, s, Fig. 27); 

 next to these, on their outer side, are scalarif orm and pittec 



Fio. 27. — A longitudinal radial section of the bundle in Fig. 26. 



vessels {t, t, g,g, Fig. 26; I, t, t'. Fig. 27), intermingled with 

 elongated cells, whose walls are pitted (A, h', h", h'", Fig. 

 27). The last-named are clearly related to the vessels 

 which surround them, and from which they differ only in 

 their less diameter, and in having imperforate horizontal 

 or oblique partitions. They are doubtless properly classed 

 with the tracheids (see paragraph 52). 



82. On the outer side of the tracheary portion just de- 

 scribed lies a mass of narrow, somewhat elongated, thin- 



