Vascular System of the Genus Equisetum . 
213 
the lateral 
determine the order of differentiation of the elements in 
bundles. 
It was thus clearly made out that- the spiral and annular elements 
occur nearest to the carinal protoxylem, and that those subsequently 
differentiated occur nearer to the periphery of the stem and more remote 
from the canal. 
The metaxylem strands of successive vegetative internodes are not 
directly continuous, but are 
linked together by means of 
the short, coarsely reticulate 
nodal tracheides, and no indica- 
tion was found of any of these 
strands crossing the outer sur- 
face of the nodal xylem, as 
has been suggested by Gwynne- 
Vaughan (9) for E. hiemale and 
E. maximum. The direct re- 
lation between the carinal pro- 
toxylem and the lateral meta- 
xylem in the internode of the 
aerial shoots is not very clear 
owing to the separation in 
space and time between their 
respective developments. Fur- 
ther reference will be made to 
this, however, when the structure 
of the tubers and cones has been 
described. 
In the course of an ex- 
amination of some young vege- 
tative axes of E. maximum , the 
large nodal tracheides described 
and figured by Sykes (11) were 
met with. They form quite 
early in the life of the shoot, 
and are clearly ordinary nodal tracheides which owe their shape to the 
opportunity of free development afforded by their projection into the lumen 
of the canal. They are undoubtedly concerned with the transference of 
water from the carinal canals of one internode to those of the internode 
above, as Miss Sykes suggested. 
Text-fig. 8. Diagram illustrating late develop- 
ment of the metaxylem. Length of internodes much 
reduced. 
