168 PRACTICAL BOTANY. 



parenchymatous cells, with cellulose walls, and often 

 containing chlorophyll. 



6. The Phloem, the most prominent elements of 

 which are long narrow structures with cellulose walls 

 and sparing contents : these are regarded as the repre- 

 sentatives of the Sieve-tubes. 



7. The Xylem, the most prominent elements of 

 which are spiral and scalariform Tracheides, similar 

 to those composing the xylem of the bundle in the 

 Ferns (see below, p. 195). The walls are lignified and 

 thickened, and marked by elongated pits, which by their 

 regular arrangement give the scalariform character to 

 these elements. 



Y. Cut transverse sections of a Rhizophore, mount 

 as before, and observe that (1) the peripheral tissues 

 are not unlike those of the stem, and are marked off 

 from the central cylinder by a somewhat irregular 

 Bundle-sheath : (2) that the arrangement of tissues of 

 the central cylinder differs both from that of the stem, 

 and that usual for root-structures, there being but one 

 group of Protoxylem (monarch), which is placed 

 laterally, and the later formed Xylem forming together 

 with it a central mass, which is surrounded by Phloem 

 except at the point opposite the protoxylem. The 

 structure of the individual vascular elements is similar 

 to that in the stem. 



If successful median longitudinal sections be cut through the 

 apex of a rhizophore it will be found that there is no root-cap. 

 Further, by comparison of a number of sections, both longitudinal 

 and transverse, it may be concluded that there is one apical cell 

 having approximately the form of a quadrangular pyramid. 



VI. Cut transverse sections of a Root, and mount 



