624 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou VI. 
ing an astelic central cylinder. The writer has been able to confirm the 
existence of individual phlceotermal sheaths about the fibro-vascular 
strands in this species ; but, unfortunately, in the young plants available, 
the older region of the stem had already disappeared. Van Tieghem* 
does not give any account of the development of the cauline axis of 
Aroids in his well-known memoir on the anatomy of the order. 
In Calla palustris, the young epicotyledonary stele is pithless until 
after the exit of the second leaf-trace (including that of the cotyledon); 
just below the point where the fibro-vascular supply of the third leaf is 
given off, the central cylinder becomes tubular. The traces of the coty- 
ledon and the first leaf are single ; but three bundles pass out into the 
petiole of the third leaf. The three traces of the third leaf subtend 
three foliar gaps in the central cylinder, which usually close at the fourth 
node. <A continuous fibro-vascular tube thus appears at the node of the 
seedling similar to that figured by Van Tieghem* as occurring at the 
nodes of the mature rhizome. Above this node the fibro-vascular cylinder 
“is perforated again by gaps corresponding to traces of the fourth leaf, 
which are likewise three in number. The writer has had the opportunity 
of following the development of this species in specimens of not more 
than six nodes. The traces of the sixth leaf are three in number, as are 
those of the third, fourth and fifth. From the level of exit of the traces 
of the third leaf, the fibro-vascular cylinder is astelic in Van Tieghem’s 
sense. The fundamental tissue forming the core of this cylinder is at 
this stage not traversed by any so-called medullary strands, so that the 
young central cylinder in this species closely resembles that of a Dicoty- 
ledon such as Ranunculus acris. The individual strands are likewise in 
the young plant collateral, and the so-called amphivasal concentric 
strands make their appearance subsequently, as the writer has been 
able to learn from somewhat older seedlings, which had already lost 
the primary region of their stems. 
The base of the young shoot in Symplocarpus fetidus is tuberous, as 
is often the case in the Aroids. Photograph 11, plate 8, represents part 
of the ring of fibro-vascular bundles as it appears about half a centi- 
metre above the base of the tuber. The individual bundles are collateral 
at this stage, and by treating sections with strong sulphuric acid, the pres- 
ence ofa cutinized phiceoterma may be demonstrated. The phlceoterma 
appears in the form of sheaths surrounding the separate bundles and 
hence the fibro-vascular cylinder in this phase of development is astelic. 
If a section be made through the young axis in the region where the 
47- Ann, Sci. Nat. Bot., 5 ser., 6 tom. Recherches sur la Structure des Aroidées. 
48. Op. Cit., plate 4, fig. 5. 
