Anatomy of the Ophioglossaceae. III. 9 
represented, but soon ceases to be recognizable in the bundles of the base 
of the leaf. 
The stage represented in Text-fig. 3, c, is evidently that recognized by 
Bertrand and Cornaille 1 as an ‘ etat tres particulier de la trace clepsydro'fde *, 
but not described or figured in full. They describe it as ‘ une chaine binaire, 
celle-ci est doublement fermee, etant composee de deux divergeants fermes \ 
The name given by these investigators to this stage will be adopted, and 
the significance of this clepsydroid stage will be discussed later. As a rule 
it is passed through rapidly, the complete division of the trace being effected 
in the outer part of the cortex. 
The actual appearance of the large trace, the structure of which has 
been represented in Text-figs. 2 and 3, is shown in PI. II, Photos 20, 21, and 
PI. I, Photos 5 and 6. In Photo 21 the nascent trace is seen to the left, still 
forming part of the stelar tube. Photo 5 shows the adaxial completion of 
the xylem of the separated trace almost effected, while Photo 6 shows the 
trace in the clepsydroid stage. The low-power photograph in PI. I, Photo 4 
shows the trace in the clepsydroid stage in relation to the stele, from which 
it had departed. 
This large trace, derived from a full-sized adult stele, has been 
described at some length, since it allows the distinction to be clearly made 
between the mesarch condition , i. e. the existence of outer and inner xylem 
corresponding to the outer and inner xylem in the stele of the rhizome, and 
the essentially different condition brought about by the adaxial completion 
of the outer xylem in the leaf-trace. Since the mesarch condition persisted 
until after this trace divided, the adaxial completion of the arc of outer 
(centrifugal) xylem could be seen to be quite distinct from the original 
mesarchy. The distinction of these two constructions, both resulting in the 
presence of metaxylem to the inside as well as the outside of the proto- 
xylem, must be borne in mind in considering other examples, the interpreta¬ 
tion of which is less obvious. 
Different pieces of rhizome, while agreeing in the general type of con¬ 
struction of stele and leaf-trace, exhibited variants of the type, which were 
usually maintained throughout the particular piece of rhizome. These 
variants are of special interest in the leaf-trace and concern its mode of 
departure, its construction in the cortex, and its mode of division. Some 
examples will now be briefly described and illustrated in order to show the 
nature of the range. 
The division of the leaf-trace often takes place without the adaxial 
completion of the xylem or endodermis having been effected. This is 
found both in the case of leaf-traces that are mesarch at their departure 
and in the case of smaller traces that have no centripetal xylem. An 
example, though not an extreme one, of a dividing trace, in which the 
1 Loc. cit., p. 179, foot-note. 
