240 



BOTANICAL GAZETTE 



[march 



long as broad, and rounded at the ends. The spools between, 

 forming their borders, show a fairly thick, secondary, unlignified 

 wall, ridged in most cases by one to two lignified (shaded) bars. 



small, and the primary 



them 



Fig. 14. — Botrychiiim obliquum: tangential section of the rhizome showing 



pitting; X600. 



similar 



toward the top of the figure. 



These are shown on the last four spools 



stem wood of Helm 



similar 



To the 



right of the center the walls of two adjacent tracheids have been 



cut in section. 



com 



in 



that 





to the right, of tertiary bars as well, 

 these bars may be seen in the tra< 



gement 



first-formed elements of the metaxylem of both Helminth 

 fS and Botrychium show less of a tertiary layer than the lat< 



