3 82 



STUDIES IN FOSSIL BOTANY 



partly filled up by the intercalation of intermediate 

 strands of secondary wood and bast. The activity of 

 the cambium was, in fact, in all respects normal ; the 

 secondary wood and bast agree in structure with the 

 corresponding tissues in the stem. No distinct formation 

 of periderm has been observed in these roots. 



Fig. 142. — Lygiuodcndrou oldhamhtltt. Part of radial section of stem, showing an 

 adventitious root, which is so curved as to be seen partly in longitudinal, partly in 

 transverse section, .v", secondary wood of stem ; />c, pericycle ; o.c, outer cortex ; 

 a, connection between root and wood of stem ; rt, root, in transverse section, showing 

 tetrarch structure, and giving off a rootlet. X 9. S. Coll. 466. (G. T. G.) 



It is certainly a fact of great interest that the roots 

 of our fossil, which, in their primary condition, much 

 resemble those of recent Marattiaceous Ferns, or of 

 Helminthostacliys among the Ophioglossaceae, should 

 exhibit a mode of secondary tissue-formation absolutely 

 indistinguishable from that of typical Dicotyledons or 

 Gymnosperms. 



Naturally, all the roots of Lyginodendron with which 



