1 7 6 Scott. — -On some points in the Anatomy of 
is due to the presence of two great masses of secondary 
tissue, chiefly xylem, which have been added one on each side 
of the stem. The original ring of xylem can be traced all 
round ; at the flat sides it has received little or no increment, 
while on the prominent faces the additional masses of wood and 
bast have been superposed upon it. The xylem of these 
masses is characterized by the presence of many enormous 
pitted vessels, attaining -25 mm. in diameter, while those of 
the ordinary ring scarcely measure -05 mm. The phloem 
is decidedly more developed on the prominent faces than 
elsewhere, but the difference is not so marked as in the 
xylem. 
The flattened region extends to the hypocotyl, in which the 
median line of the prominences is at right angles to the plane 
of the cotyledons. Towards the root, however, the thickening 
becomes more uniformly distributed until the transverse 
section is once more circular (Fig. 2). 
In the upper part of the flattened region there is nothing 
anomalous except the unequal distribution of the secondary 
tissues, which also occurs in some other Convolvulaceae. A 
little thin-walled parenchyma is present in the secondary 
xylem. 
In the lower internodes, however, the structure is much less 
regular and in the hypocotyl is extremely anomalous (cf. Fig. 
2). The secondary masses of wood are broken up in all 
directions by bands and patches of thin-walled parenchyma 
containing isolated strands of phloem, in which the sieve- 
tubes and companion-cells are of normal structure, and per- 
fectly similar to those of the external and medullary phloem. 
The diagrammatic section in Fig. 2 is taken from the lower 
part of the hypocotyl where the secondary thickening is 
nearly uniform all round. The parenchyma of the wood, 
whether forming rays or isolated groups, is everywhere tra- 
versed by strands of phloem. In these transitional regions a 
large proportion of the whole phloem is interxylary. 
The investigation of developmental stages leaves no doubt 
that these masses of parenchyma, together with the phloem 
