550 Brebner . — On the Anatomy of 
stele developed from a non-medullated haplostele by an early 
formation of overlapping leaf-gaps accompanied by branching 
and anastomozing of the meristeles. 
The only point in which Danaea differs essentially from 
Angiopteris and Marattia is in not passing through a medul- 
lated stage before the commencement of the formation of the 
dictyostele. There can be little doubt that Kaulfussia and 
Archangiopteris pass through a similar stage, and in a very 
similar manner. 
Comparative Anatomy of the Marattiaceae. The result of 
the study of the comparative anatomy is broadly that there 
is a great amount of uniformity in internal structure. They 
are all adelosiphonous with a greater or less tendency to dor- 
siventrality in Angiopteris , Marattia and Danaea. In the 
last-named it is distinctly marked and practically complete 
in Kaulfussia (Kuhn, and Farmer and Hill). In the young 
sporophyte of the three first-named the symmetry is radial. 
The meristeles of the stem and leaf are practically identical 
in structure. The veins of the first leaf are collateral, as also 
the ultimate ramifications of the veins of the young and adult 
fronds. 
The protoxylem seems to be normally endarch and mesarch 
in the stem, endarch in the frond. A very imperfect mesarch 
condition also quite exceptionally occurs in the larger leaf 
meristeles, and occasionally in the fine veins. 
The root-structure, as already stated, is practically identical 
throughout the family. The aerial roots of Angiopteris 
and Marattia are polyarch and their subterranean portions 
oligarch. In Danaea alata , and presumably many others, the 
adult roots are polyarch. In Angiopteris there are very 
thick sclerotic cells sparingly present in the cortex and there 
is a mid-cortical ring of sclerenchyma in Danaea. Danaea 
also has a medullary strand of sclerenchyma fibres, which 
differentiate very early. The roots of Archangiopteris and 
Kaulfussia were not examined, but the latter are described 
by Kiihn and are tetrarch to pentarch, but not otherwise 
essentially different. 
