•LYGINODENDRON 



379 



are beautiful objects, showing the characteristic points 

 of root-structure with diagrammatic clearness. Some 

 of the specimens are still in their primary condition, 

 while others show the secondary tissues at all stages of 

 their development. Some of the smallest rootlets are 



Fig. 141. — Lyginodendron oldhamium. Transverse section of root, somewhat diagram 

 matic. px, one of the protoxylem-groups ; jr, the heptarch primary wood ; jr 2 

 secondary wood ; J>h, phloem; i.c, inner cortex; o.c, outer cortex; rt, rootlets, 

 opposite two protoxylem-groups. X 24. Founded on S. Coll. 448. (G. T. G.) 



triarch, or even perhaps diarch, but the larger and more 

 characteristic specimens have from four to eight initial 

 groups of xylem, alternating with as many strands of 

 phloem. The root shown in Fig. 141 was a heptarch 

 one. The primary wood has a well-marked stellate 

 form, as seen in transverse section (see Fig. 141). The 

 smallest tracheides, which are shown by longitudinal 



