Anatomy of Solenostelic Ferns: I, Loxsoma. 95 
Summary. 
To sum up shortly, the principal features of the anatomy 
of Loxsoma and the conclusions resulting from their con- 
sideration may be stated as follows : — 
1. The stem is typically solenostelic. 
2. A single vascular strand is given off to each petiole 
having the form of a horseshoe, the xylem being of the same 
form, and hooked at the ends. 
3. In the stem the protoxylem-elements, which are all 
scalariform, are not localized into definite groups, but are 
distributed around the external periphery of the solenostele. 
4. In the petiole the protoxylem-elements, which are spiral 
and annular, are collected into definite endarch groups, but 
they are not continued down into the solenostele of the stem. 
5. Parenchymatous islets are found in the .sclerenchyma 
of the stem, and intercellular rodlets in the tissues of both 
stem and leaf. 
6. Sclerosed fibres and cavity-parenchyma are present 
in the vascular strand of the petiole. 
7. By its anatomy Loxsoma is more nearly related to the 
Dennstaedtiinae and the solenostelic Polypodiaceae than to 
any other family of Ferns, although affinities of a more 
remote nature to the Gleichen iaceae , Schizeaceae, and Hymeno- 
phyllaceae are also indicated. 
Conclusion. 
In reviewing the anatomy of a number of Fern-petioles 
I have been greatly impressed by the fact that the plan of 
the vascular arrangement in the petiole is almost invariably 
referable to a single universal design, that which I have described 
as resembling a horseshoe. So much, indeed, is this the case 
that I have been led to regard it, with some notable exceptions 
( Lygodium , Schizaea , Marattiaceae , &c.), as fundamentally 
typical for the Filicales. In many cases, of course, the 
