35i THE STRUCTURE OF ECONOMIC PLANTS 



Some variations have been noted with respect to the arrangement 

 of the vascular strands in the epicotyl. In some cases, the medul- 

 lary xylem does not anastomose to form a solid core; but, after the 



'6ct2 



First Internode 



Third Internode 



Second Internode 



Fourth Internode 



Fig. 178. Diagrammatic transections of first four internodes. Protoxylem is repre- 

 sented in solid black, metaxylem lined, phloem stippled, and phloem and cortical fibers cross- 

 hatched : bet 1 and bet 1, first and second trifid bracts; co bu, cortical fibrovascular bundles; 

 /-3, /-4, /-J, traces to foliage leaves; /ac, lacunae; ttt bu, stipular bundle. 



first tangential fusion into two lateral bands, may break up into 

 eight groups again. In other instances, the lateral phloem groups 

 reunite so that there may be only two or three strands within the 

 endodermis instead of four. 



