267 
Archangiopteris Henryi and other Marattiaceae. 
are endarch in both stem and petiole. The phloem extends all round the 
meristeles of the stem, but protophloem occurs only on the outer side of 
the xylem, and there, as described by Miss Shove in Augiopteris , it lies 
between the xylem and the metaphloem. This extraordinary fact can be 
observed with perfect clearness in all the strands, external or internal, of 
both stem and petiole, and even in those of the stipule. The cells of 
phloem-parenchyma in immediate contact with the sieve-tubes are small 
and have albuminoid contents. A layer of large cells usually containing 
starch intervenes between the protophloem and the metaphloem, and two 
or three layers of similar cells separate the former from the xylem. The 
two cell-layers immediately surrounding the phloem are slightly different 
from the rest of the ground-tissue of the stem both in their form and in 
their reactions towards staining reagents. They might, perhaps, be regarded 
as a pericycle, but since neither an external nor an internal endodermis 
could be demonstrated in either stem or petiole, it is impossible to set any 
definite limit to the vascular strands. As in the rest of the order, there 
is no sclerotic tissue of any sort in the stem, but in the petiole there is 
a layer of fibres with colourless lignified walls situated a few layers below 
the epidermis. In the pulvini this fibrous layer is replaced by a zone of 
collenchyma. It is, perhaps, also worth mentioning that a certain amount 
of sclerotic tissue, quite different in nature from that of the fibrous zone, 
is to be found in the upper part of the rachis in the form of Marattia 
fraxinea that I examined. It consists of short rectangular elements with 
very thick pitted walls ; something like stone cells. They form a very 
irregular and incomplete sheath around the vascular strands, separated from 
the phloem by two or three layers of thin-walled parenchyma. 
Mucilage canals occur irregularly distributed in the stem, root, and 
petiole. In the latter they are confined to the tissue within the fibrous 
zone, except in the pulvini, where they also occur between the collenchyma 
and the epidermis. Tannin sacs are present in the petiole, but not in 
the stem. The paleae which occur at the base of the petiole arise from the 
bottom of deep pits. They are lanceolate in form, with a toothed margin, 
and run out into a long narrow point. 
General Conclusions. 
In forming any conclusions based upon this account of the structure of 
Archangiopteris it is necessary to bear in mind that a small portion of 
a single plant only has been examined, and that, since a comparatively small 
specimen would naturally recommend itself to a collector as convenient for 
manipulation and transport, it may quite well be that this particular speci- 
men does not represent the full size attainable by the species. It is possible, 
therefore, that other specimens may disclose a structure considerably more 
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