Harriet H. Allisotl. 
3 li> 
the foliage-leaves, are inserted in two rows upon the axis, a series 
of nest-leaves alternating with a series of foliage-leaves. Fig. 1, 
a side view of the rhizome of P. alcicorne, shows the leaf bases of 
a series of foliage-leaves, and also the bases of the decayed nest- 
leaves, which closely invest the axis and act as a protection for the 
younger leaves. On the ventral surface, the dark covering of rootlets 
was removed in order to show the vegetative buds, which arise at 
the bases of the leaves as brown swellings. 
The young plant of P. alcicorne shows a condition more nearly 
approaching the simple dictyostelic types of fern than any of the 
other specimens examined. The plant described was a small 
tuberous one about 3 mm. in diameter, and serial sections were cut 
through several leaf bases up to the apex. The apex is protected 
by hard brittle hairs, which have become expanded into elongated 
scales. These scales consist of two rows of cells, with a hard 
brown substance between, which extends the length of the scale. 
In this plant, one leaf had expanded and the petiole has a ring 
of five or six vascular bundles, embedded in a ground-mass of 
parenchyma. Surrounding these strands is a ring of smaller, 
sharp-angled cells, which show slight thickening on the walls and 
later form a band of sclerenchyma, external to the narrow-celled 
endodermis. 
The relation of the leaf-trace to the vascular system of the 
axis is simpler and more easily understood than in the older plant. 
The whole rhizome is covered with elongated scales, and on the 
ventral surface rootlets pursue an oblique course through the 
cortex. The ground-mass of the axis consists of thin-walled 
parenchymatous cells, but here and there thickenings on the cell- 
wall forecast the sclerenchymatous ground-mass of the mature 
plant. The vascular system of the axis is a dictyostele consisting 
of eight or nine meristeles, which anastomose frequently. On the 
inner face of each meristele a cap of sclerenchyma is found. The 
leaf-trace, which in the petiole becomes a ring of six vascular 
bundles, consists, at first, of two strands only (Fig. 2, 4). One of 
these meristeles divides into two strands, from which the vascular 
system of the vegetative bud at the base of each leaf is derived 
(Fig. 2, 6-10). Meantime, the adjoining strands of the dictyostele 
extend across the leaf-gap, and form a commissure (Fig. 2, 9, 10). 
This commissure is temporary, however, and almost immediately 
divides to form two more strands of the leaf-trace. The leaf-gap is 
practically closed by a long meristele. At this point the leaf-trace 
