THE GROUPS OF TISSUES, OB TISSUE-SYSTEMS. 49 



as it is placed in the stem) is a mass of sieve-tissue, com- 

 posed of latticed cells {v, v, Pig. 30). Surrounding the 

 whole is a thick mass of fibrous tissue composed of elon- 

 gated, thick- walled cells (the shaded ones in the figure). 



83. In the Castor-oil Plant the limits of the fibro-vascu- 

 lar bundles are so poorly marked that in places it is impos- 

 sible to tell whether the tissues belong to them or to the 

 surrounding ground-tissues. The inner portion of the 



Fig. 32.— a longitudinal radial section of the bundle in Fig. 31. 



bundle {g, g, t, t. Fig. 31, and s to t, Fig. 32, is made up 

 of tracheary tissue of several varieties; on the inner edge 

 of this tracheary portion lie several spiral vessels (s, s. Fig. 

 33) ; next to these, on their outer side, are scalariform 

 and pitted vessels {t, f, g, g. Fig. 31 ; I, t, t' , Fig. 32), 

 intermingled with elongated cells, whose walls are pitted 

 (A, V , Ji", h'", Fig. 32). The last-named are clearly re- 

 lated to the vessels which sufround them, arid from which. 



