Vascular System of Matonia pectinata . 493 
passes into the forward. In this group the connexion takes place by 
the more or less sudden passing up of a column of tissue from the second 
cylinder to this point. Secondly, those in which the connexion takes place 
further forward, sometimes after the complete departure of the trace. 
In this group the connexion occurs by the gradual raising of the roof 
of the second cylinder till its sides come into contact with the bases of 
the backward curls of the leaf-trace. 
The first type of connexion between the rhizome cylinders and the 
petiolar bundle in 4 adult 5 plants is found, as might be expected, in the 
smaller dicyclic forms. It is essentially similar to cases G and H. 
In the simplest case of this group (Stage X) the final f forward curl ’ of 
the leaf-bundle is not continued down to its actual insertion on the 
rhizome stele, and, as in the last-described case, the second cylinder merely 
sends up a column of tissue (median, or first on one side, according 
as the trace is attached symmetrically or asymmetrically) to supply the 
backwardly directed limbs of the trace and to fill the gap h The tracheids 
at the outer limits of this column, on each side, sometimes end in a kind 
of notch (equivalent to the ‘ gutter * in more advanced forms), which 
is continuous above with the forward curl of the trace. 
In the next case (Stage XI) the forward curl of the leaf-bundle is 
continued down to the point of attachment, and then the ascending column 
of tissue from the second cylinder branches on each side into an inner 
and an outer limb, supplying respectively the backward and the forward 
curl of the trace (Plate XXXIII, Fig. 29). 
The three cases of this group are found in quite small rhizomes, 
with an outer cylinder of 2-1 mm. average diameter and an inner of -8 mm. 
The second group of cases (Stage XII) represents the great majority of 
the adult rhizomes. It numbers forty-four nodes, and the outer vascular 
cylinder has an average diameter of 3-7 mm. A third cylinder occurs 
in forty-two out of the forty-four cases. The cylinders are much further 
apart in this group than in the preceding one. Consequently the connexion 
of the second cylinder, owing to the gradual raising of its roof, with the 
first, takes place much further forward, often in front of the anterior roots 
of the leaf-trace ; and the tracheal supply from the second cylinder to the 
leaf-trace is consequently directed sideways (or even backwards) and 
upwards instead of forwards and upwards. A final elaboration of the 
leaf-trace connexions must now be mentioned. The bases of the free 
forward curls of the trace are continued forwards as outwardly turned 
1 The mode of connexion between the second cylinder and the lateral loops of the leaf-trace is 
decidedly variable in this type. In one case, for instance, the second cylinder sends up a mass of 
tissue in the form of two arms which pass back and join together to form a median bulge in con- 
nexion with the lateral loops of the trace ; this then passes forward again, still in connexion with the 
loops, but above the original arms, and finally becomes the compensation-tongue which closes the 
gap in the outer cylinder. 
