616 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou VI. 
The young stem of &. acrzs has a stelar system very much like that of 
Botrychium Lunaria, t.e., it consists of a fibro-vascular tube pierced by 
foliar gaps. Through the latter, the internal phlocoterma, which is ex- 
tremely well marked in the young stem of this species, communicates 
with the external phloeoterma. Photograph 13, plate 9, shows a leaf- 
trace passing off from the stelar tube, and subtending it is the foliar gap. 
The continuity of the internal and external phloeotermal layers through 
the foliar gap can be easily distinguished. The photograph in this case 
was made froma section treated with phloroglucin and hydrochloric acid, 
which causes the lignified phlceoterma to stand out sharply. The stelar 
tube, as in the case of the young so-called polystelic axes, only becomes 
fully established after several leaf-traces have been given off, including 
those of the cotyledons, and at first, as in the young stem of Przmula 
farinosa, the tube contains only enclosed pericycle and no fundamental 
tissue. The leaf-traces to each leaf are originally single, but very soon 
become three in number : a central large one and two smaller lateral ones. 
The departure of the median trace causes a large gap in the stelar tube, 
through which, the internal and external phlceotermal layers communi- 
cate. The lateral strands cause smaller breaks in the continuity of the 
fibro-vascular cylinder and frequently the internal and external cortex do 
not become continuous through them. The gaps, as a result, are occu- 
pied merely by pericycle. The stelar cylinder in the more advanced 
young stem is characterized by the overlapping of the foliar gaps, so that 
in a cross section it appears as a circle of separate bundles. This state 
of affairs is shown in photograph 14, plate 9. Somewhat higher up in 
the young stem, the overlapping foliar gaps become more numerous, 
both on account of the increased number of leaf-traces given off to each 
leaf and the greater elongation of the individual foliar gaps. For 
this reason, the stelar tube, in transverse section presents the appearance 
of a number of separate vascular strands, the fibro-vascular bundles, each 
of which is surrounded by it8’ own phlceotermal sheath. In older regions 
of the stem, the fibro-vascular strands of the leaf-traces dip inwards and 
pass outwards again, thus simulating the peculiar course of the leaf- 
traces which becomes the rule among the Monocotyledons. 
From the thick parenchymatous hypogeous stem of &. acrzs the 
more slender aerial shoots originate. - Since the latter must support, in 
spite of their comparative delicacy, a considerable weight of leaves, 
flowers, and fruit, the mechanical tissues which are scarcely present at 
all in the subterranean stem, are well developed in the epigzeous shoots. 
As is well known, the mechanical tissues of FR. acris appear as fibrous 
sheaths around the individual bundles. Already, in the older subter- 
