1922] BROWNE—EQUISETUM | 449 
ends and flanks of the lateral bands of metaxylem. This phase 
is represented in fig. 1, stage 3. During these and the two subse- 
quent stages figured, certain partially torn elements of protoxylem 
may be found adhering to the carinal canal. Their presence is 
Fic. 1 
part of inten: region Thee shown as black and aasiciks as broken line): cc, geet 
Cavity of axis; vc, vallecular canal; car.c, carinal canal; px, protoxylem; st, small 
tracheids of metaxylem; p. phi, protophloem; px.tr, protoy lem of trace; mx.tr, mi 2 meta- 
sta of trace; ps, trace; 
X12 
very inconstant; they may be absent from many consecutive 
sections, nor is their frequency correlated with the increase in 
xylem which continues as the node is approached. : 
As we pass upward, the tracheids of the crossbar increase in 
number and size, especially in its median region, where the increase 
