622 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
internal and external series of strands, and the stelar tube can no - 
longer be recognized as such. Photograph 23, plate 10, represents a — 
section of the young stem of Wuphar advena in a region where the 
leaves have numerous traces and the stelar tube, as a consequence, is 
broken into many segments. 
The young stelar system of Nymphaea szanzibarensis is at first a 
pithless strand, but very rapidly becomes tubular with usual foliar gaps. 
Quite early all semblance of the original stelar tube vanishes on account 
of the appearance of complexly anastomosing internal and external 
systems of fibro-vascular strands. 
The young stem of Mymphea tuberosa has also been studied by the 
writer. The epicotyledonary central cylinder is originally pithless, as 
in the other nymphzeaceous species already described, but rapidly 
expands and almost immediately breaks up into an extremely complex 
system of anastomosing bundles, so that it is extremely difficult to 
recognize the existence of a stelar tube. Towards the end of a season’s 
growth, however, the stelar tube again becomes obvious in the more 
slender region of the stem which is formed during the autumn. The 
stelar tube in this case has an internal phloém as well as an internal 
phleeoterma. The tubular condition is probably to be regarded 
as a reversion to the primitive type of stelar system, and may be 
compared with that noticed by Gwynne-Vaughan* in the autumnal 
region of the stem of Primula obtusifolia and P. tnvolucrata. In 
another essay this writer has described the occurrence of concentric 
fibro-vascular strands in slender pedicles of the tubers which are so 
characteristic a method of vegetative reproduction in this species. I 
have examined the structure of the pedicles in question and have 
confirmed the existence of the concentric strands described by Gwynne- 
Vaughan. The fibro-vascular tissues in this case form a tube with foliar 
gaps, a fact which seems to have escaped his notice. As the slender 
pedicle passes into the tuber, the tubular concentric stele vanishes in an 
extremely complex system of anastomosing strands, some of which are 
concentric while others are merely collateral. The reappearance of 
the tubular stelar system, in the autumnal region of the young 
rhizome and in the pedicles of the tubers is interesting as a probable 
case of reversion. The base of the lateral shoots of the rhizome of 
Pteris aquilina not unfrequently shows a reversion to the more primitive 
tubular stele with a single medullary strand. The writer has found a 
similar concentric tubular stelar system in the pedicles of Vymphea 
dentata. 
45. Op. Cit., p. 300. 
46. \nn. Bot., v. 10, p. 290. 
