Anatomy of the Cone and Fertile Stem of Equisetum. 669 
and 3 of the third order. It will easily be realized that the persistence 
of a parenchymatous mesh through a node is the result of a poorer develop- 
ment of xylem. Thus Cone C has relatively less xylem than Cones A and 
B. For instance, the presence of a very little more xylem between the 
Text-fig. 2. Longitudinal reconstruction of the xylem of Cone C of E. arvense. Axial xylem 
black; leaf-traces and parenchyma white. Magnification circa 12. 
fifth and sixth traces of the second whorl of Cone A would lead to the 
division of a parenchymatous mesh of the second order into two meshes 
of the first order. When the xylem developed at a node is less markedly 
deficient, the mesh that persists appears to be sharply constricted in the 
nodal region ; when, on the other hand, the strands show little or no 
