Anatomy of the Cone and Fertile Stem of Equisetum . 68 1 
in reality developed, and the parenchymatous meshes tend to dovetail into 
one another at the nodes, since those of the upper internode originate before 
those of the lower one are closed. In a longitudinal reconstruction of the 
xylem, the width of the latter at the node is increased by the fact that when 
the branches of a strand diverge obliquely the vessels are, of course, cut 
obliquely. A tendency for the parenchymatous meshes of the internode 
below not to be closed until after the origin of those of the internode above 
may be noted occasionally in the cone of E . arvense y and now and then in 
Text-fig. 7. Different forms of course of the strands at the nodes. 
the vegetative nodes of the three species that I studied ; but it does not be- 
come a marked feature in any of them. According to Pfitzer (Pfitzer, p. 344) 
this type of alternation, shown in Text-fig. 7, B, is found in the vegetative 
nodes of E. variegatum. 
In E. limosum , however, it is unusual, except in the fifth and sixth 
whorls of Cone A, for two or more adjacent strands to give off median 
traces and fork above their departure. Much more commonly one strand 
forks and its neighbour does not ; in such cases we get an irregular anato- 
mical alternation between members of successive whorls. Of this irregular 
