606 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
representatives of this group have led to the conclusion that the young 
central cylinder of this type is always tubular, and that there is no 
indication of the bifurcation of the primitive fibro-vascular axis. 
Photograph 2, plate 7, shows the older stelar tube of P. aguzlina, 
where it is provided with an axial core of fundamental tissue. At a@ is. 
to be seen the foliar gap corresponding to the leaf-trace 7? ; v is a root, 
and /! an earlier leaf. When about a dozen leaves have been formed, 
the vertical young stem of P. aguzlina bifurcates, or in some cases 
trifurcates, and the resulting divisions plunge into the soil and pursue a 
subterranean horizontal course. Leclerc du Sablon” has made a 
curious mistake in regard to the mode of origin of the horizontal rhizome 
of this form. He describes it as originating from a bud in the axil of one 
of the leaves of the vertically-growing young plant. The writer has seen 
the bifurcation of the stem regularly occurring in many hundreds of 
examples of plants grown from different lots of spores and in different 
years; so that there can be no doubt that it is a quite normal process. 
The writer’s account, moreover, agrees exactly with the older description of 
Hofmeister’. Photograph 3, plate 7, represents a section of the young 
stem just above the bifurcation of the stelar system; a@ and 0 are the 
tubular steles which are about to pass into the two horizontal 
rhizomes. The stele a has just given off a leaf-trace/; in 4 the foliar gap 
is also still open. - Shortly after the young rhizomes make their 
appearance, the leaves, which at first originate at small intervals, become 
more widely separated, and their foliar lacune frequently overlap. For 
this reason, in a cross-section of the stem at this stage, one often sees an 
appearance of independent dorsal and ventral steles, as in photograph 4, 
plate 7. A series of sections, however, show that the stelar system is 
still tubular. At this stage, a strand of brown sclerenchyma becomes 
evident in the centre of the stelar tube, and, a few centimetres further 
on, the ventral wall of the latter becomes involuted. A fibro-vascular 
strand is subsequently detached dorsally from the involution, and forms 
one of the two large axial concentric bundles found in the mature 
rhizome. The single central strand is rapidly surrounded by a 
sclerenchymatous tube formed from the sclerenchymatous rod described 
above. This stage is represented in photograph 5, plate 7, Subsequently, 
a second central strand is detached dorsally from the ventral wall of the 
stelar tube. This strand is at first small, but ultimately becomes nearly 
as large as the first-formed strand (fig. 6, plate 7). The two axial 
concentric strands contribute to the formation of the leaf-traces, but 
have no connection with the vascular supply of the roots. 
T6Op, Cits ups se 
17 Higher Cryptoganis, Ray. Soc., p. 214. 
