388 Boodle. — On some points in the 
xylem-elements are at the inner limit of the strands ; that 
is, the bundles are endarch. This is an important character, 
because, as Professor Farmer informs me, the vascular ring 
in the rhizome of Helminthostachys is distinctly mesarch. An 
examination of some material of the mature rhizome of 
Helminthostachys 1 led me to the same conclusion. 
There is a considerable amount of secondary thickening at 
the bases of many of the roots of Botrychium Lunaria , where 
they are immersed in the cortex of the stem. This some- 
times makes it impossible to tell the position or number of 
protoxylem-groups, as one sees in the case of Fig. 14. For 
this reason some of the series of sections cut to determine the 
orientation of the root-stele at its junction with the stem- 
bundle were useless. 
The well-known secondary thickening in the stem of 
Botrychium Lunaria makes it not surprising to find a trace 
of it in the stem of Ophioglossum vulgatum , but secondary 
thickening was hitherto unknown in the root of any recent 
Pteridophyte. 
In the petioles of unfolded leaves of Ophioglossum vulgatum 
the vascular bundles sometimes show developing tracheides 
(as in Fig. 12), but it seems uncertain whether these should 
be regarded as secondary or not. 
Conclusion. 
Some of the works on Ophioglossum have been referred to 
above, but it remains to quote the results of some authors 
more in order and detail. 
The main facts as to the structure and development of the 
root of Ophioglossum vulgatum were described and figured by 
Stenzel 2 as early as 1858. His Fig. 4 (Tab. 58) is a very 
good representation of the early stage of the stele, in which 
1 Kindly sent by Mr. A. C. Seward, F.R.S. 
2 Stenzel, Unters. iiber Ban u. Wachsthum der Fame, I. Stamm u. Wurzel 
v. Ophioglossum vulgatum, Nov. Act. Acad. Leopold. -Carolin. Nat. Cur., xxvi 
(1858). 
