442 Farmer and Freeman. — On the Structure and 
results, since the youngest segment-cells often begin to pro- 
liferate and to fill up the gap left by the dying cell (see Fig. 1 6). 
Almost every root available for study was thus affected ; and if 
the process has gone on to any great extent it produces an apex 
of exceedingly singular structure, in which apparently several 
apical cells may be present. Indeed at one time we were 
tempted to compare the root of this plant with that of Angi- 
opteris 1 rather than with that of Botrychium y which, when in 
a healthy condition, it much more closely resembles. 
The root, as already remarked, branches freely, but we 
were unable, owing to the absence of suitable stages in our 
material, to ascertain whether the branches originate from the 
endodermis or from the pericycle. 
Summary. 
i 
1. Helminthostachys is dorsiventral ; the roots which spring 
from the flanks and lower side of the rhizome bear no definite 
relation to the leaves which arise from its upper surface. 
2 . The leaves are provided with stipular appendages which 
enclose the youngest leaves and pass over the apex of the 
stem, where they fit into a corresponding depression in the 
tissues. They more closely resemble the leaf-appendages of 
Botrychimn than those of Ophioglossum . 
3. The rhizome possesses a single stele. The vascular 
elements in all save the youngest stems enclose an axile pith. 
4. There is an inner irregular and an outer well-developed 
and regular endodermis. 
5. The xylem is mesarch in character and differentiates 
very slowly from the procam bial strand. 
6. There is no secondary formation of vascular tissue. 
7. Adventitious buds may be formed on the stem. 
8. The leaf-traces are single at their origin, and divide 
to the full number of petiolar bundles in the cortex of the 
rhizome. The bundles are collateral. 
1 Farmer, On the Embryogeny of Angiopteris eveda. Ann. of Bot., vol. vi. 
