13 
Anatomy of the Ophioglossaceae. Ill . 
As regards the vascular disturbance, Gwynne-Vaughan’s figure indicates 
that the inner xylem first closes across the gap, and also that the increased 
thickness of the xylem leads to the existence of a distinct low bulge behind 
and below the vestigial bud itself 
The analysis of this bulge is not carried further by him, and it is of 
interest to ascertain the parts taken in its formation by the outer and inner 
xylems respectively. This was studied in the large rhizome, the departure 
of the leaf-trace from which has been already described, and the same 
series of figures (Text-fig. 2) will serve to illustrate the anatomical relations of 
a vestigial bud in a case in which the vascular disturbance was well marked. 
After a leaf-trace has departed, the gap in the stele remains open for 
a considerable distance. On following a series of sections forward, the gap 
in the tube of xylem is seen to narrow, and its edges to thicken as prepara¬ 
tions for closure become recognizable (Text-fig. 2, A, b). The thickening is 
largely due to an increase in the amount of inner xylem, which at this 
region becomes more strongly developed than elsewhere in the stele; there 
is also an increase in the thickness of the outer xylem, so that the wood 
bulges both outwards and inwards in the region of the closing gap (Text- 
fig. 2, B). The endodermis appears raised up over the margins of the gap. 
The closure of the gap comes about by the meeting of the edges formed by 
the bulges of inner xylem. This not only joins across the gap, but the 
inner xylem appears to extend outwards into the gap still present in the 
outer xylem (Text-fig. 2, c). A little further forward (Text-fig. 2, d) the 
outer xylem is completed over this extension of the inner xylem through 
the gap. Since the outer xylem also completes the xylem of the main stele, 
it separates the projecting portion of the inner xylem from the correspond¬ 
ing tissue of the main stele. At this level, therefore (Text-fig. 2, D), the vas¬ 
cular bulge can be regarded as a rudimentary branch stele, with its own 
inner and outer xylem. Still further forward the bulge of xylem is 
subsiding, and at this level the endodermis was completed over the paren¬ 
chymatous bulge leading towards the vestigial bud (Text-fig. 2, e). The 
last section figured (Text-fig. 2, f) is immediately in front of the actual bud, 
and shows the inner portion of the canal occupied by hairs, and beneath this 
the forwardly bent portion of the endodermal bulge. The stele of the 
rhizome has resumed its normal structure, and the endodermis is complete 
around it. 
The description of this vascular disturbance just given naturally involves 
a view as to the interpretation of the structure. This interpretation has 
been reached by comparison of a number of specimens, and will be seen 
below to be supported by the nature of the vascular supply to actual 
branches. The appearance of the vascular bulge in the specimen described 
is shown in PL II, Photos 20 and 21. Photo 20 shows the dorsal region 
of the stele just after the leaf-gap has been closed by the approximation of 
