458 OPHIOGLOSSALES 
downward one of reduction. Before discussing these two alternatives, it 
will be necessary to look into the anatomy of these plants, since arguments 
on that ground have been held to be very material to a decision. 
ANATOMY. 
The roots of the Ophioglossaceae show a wide range of internal 
structure. In Helminthostachys they are tetrarch to heptarch, and most 
commonly hexarch, with central pith, alternating phloem, a large-celled 
pericycle, and endodermis. In Sotrychium the number of protoxylems 
Fic. 256. 
Ophioglossum Bergianum, Schlecht, Transverse sections of the stele of a root, the one 
showing two unequal groups of xylem, the other only one. 200. 
varies a good deal, common numbers being two and three, but it has 
been shown in &. Lunaria that roots which are diarch distally may be 
monarch near the base, In Ophioglossum, also, there is some variety, for 
in. O. pendulum diarch, triarch, and tetrarch roots have been described, 
while in this species also a monarch structure has been seen at the base 
of a rootlet: O. decipiens has triarch structure: O. padmatum is diarch. 
Most of the species of Euophioglossum have monarch roots, and this is 
conspicuously so in O. vulgatum. In O. Bergianum the structure may be 
diarch or monarch, the latter having been observed in roots close to their 
base (Fig. 256). With the monarch structure goes bifurcate branching, 
while monopodial branching is seen where the structure is more complex, 
as in O. pendulum, Helminthostachys, and Botrychium. Thus both dicho- 
tomous and monopodial branching are found in the same genus. Possibly 
dichotomy is restricted to the monarch roots: this was suggested by Van 
Tieghem, who remarks that, if the monarch root divides, we know 
beforehand that it will dichotomise.? 
It is the fashion of the time to hold that all monarch roots are 
1Compare Boodle, Azz. of Bot., xiii., p. 377, where the literature is fully quoted. 
2 Ann. Sci. Nat., V. Serie, T. xiii, p. 108. | 
