476 Bower. — Studies in the Phytogeny of the Filicales. 
13. In Loxsoma we see an isolated monotypic genus which has 
marginal sori like the Schizaeaceae, Thyrsopteris and Dicksonia , and is, 
like both of them, solenostelic, with hairs as dermal appendages. Its 
sporangia are of the Schizaeoid type, and retain the dehiscence in 
the median plane. But the sorus has become gradate as in Thyrsopteris 
and Dicksonia. Its phyletic position is probably somewhere between, or in 
relation to, these types. 
14. The Leptosporangiate Ferns (excluding the Osmundaceae which 
appear in this respect to be indeterminate) fall into two distinct series : the 
‘ Superficiales in which the origin of the sorus is constantly from the leaf- 
surface, and the 5 Marginales ’, in which it is as constantly from the margin. 
15. So far as the value of the general phyletic characters for the Ferns 
can be estimated, the criterion of position of the nascent sorus may be held 
to take precedence, in point of early origin and constancy, over any soral 
characters except the primal features of the sporangium itself, and over any 
anatomical characters of the axis derivative from the protostele. 
DESCRIPTION OF THE FIGURES IN PLATES XXXII-XXXIV. 
Illustrating Prof. Bower’s paper on Metaxya and certain other relatively primitive Ferns. 
PLATE XXXII. 
Fig. 1. Transverse section of the rhizome of Metaxya , showing the solenostelic structure and 
coarse superficial hairs, x 3. 
Fig. 2. Transverse section of the petiole of Metaxya. x 3. 
Fig* 3 * i-vi. Successive transverse sections through a rhizome of Metaxya , arranged in basi- 
petal sequence, and traversing the base of a leaf and the young bud which springs from it. For 
details see the text, x a. 
Fig. 4. Three nearly mature sori of Metaxya , photographed in surface view. Considerably 
enlarged. 
Fig. 5. Vertical section through a young sorus of Metaxya , traversing the vein below it 
transversely. The receptacle is already of considerable size, and bears hairs, while the numerous 
young sporangia, all nearly of the same age, are already initiated, x 250. 
Fig. 6. Vertical section through a sorus of Metaxya of the same age as the last, but following 
the course of the vein. The receptacle is here seen to be extended along the vein, and it bears 
numerous sporangia and hairs, x 250. 
Fig. 7. Vertical section of a rather more advanced sorus of Metaxya , showing seven sporangia 
and numerous hairs. All the sporangia are of nearly the same age. x 250. 
Fig. 8. Transverse section through the stalks of sporangia and attendant hairs in Metaxya , 
showing their relative positions and regular orientation, x 250. 
Fig. 9. i— v. Sporangia of Metaxya seen from various points of view. For details see the text, 
x 125. 
PLATE XXXIII. 
Fig. 10. Transverse section of a small runner of Hemitelia setosa, showing the solenostelic 
structure (sol), with two small medullary strands (m.s.). sct= sclerenchyma. x 2. 
Fig. it. Vertical section through the sorus of Dicksonia Scheidei, still sufficiently young to 
