84 DR. D. H. SCOTT ON THE HETERANGIUMS 
identical with H. tilivoides. Now that H. Lomaaii is recognized as a distinct 
species it becomes evident that the “ cylindricum” specimen is merely a 
form of it, a fact which Mr. Lomax realized many years ago. 
The specimen happens to be of considerable interest. There are six trans- 
verse sections (only two of which are good), two longitudinal, and one 
oblique *. The eylindrical form of the stem is preserved with little distortion, 
while all the other Dulesgate specimens are more or less compressed. The 
outer cortex has a cnrious carbonized appearance, and may have undergone 
some change which made it more resistant than in other cases. 
The best transverse section is one in the University College collection, and 
is shown in Pl. 2. Phot. 14. The Williamson section previously figured 
(Williamson & Scott, 1895, pl. 28. fig. 30) is rather less complete, though the 
cylindrical form is more perfect. The stem is 6°75 x 5 mm. in diameter. 
The primary wood is well preserved, and agrees in every respect with that 
of the specimens of //. Lomawii already described. A few layers of small- 
celled secondary wood had been added in places. Scarcely any of the phloem 
is preserved, and in the pericycle only the sclerotic nests persisi ; their 
presence, once regarded as distinetive, is of course common to the Dulesgate 
stems generally. The cortex is quite well preserved—much better than is 
usual in the 8 specimens. The masses of sclereides, with radiating cells 
round them, are conspicuous and have assumed a black colour, The 
longitudinal seetions show that they form solid blocks as in other Dulesgate 
stems. The Sparganum hypoderma has the structure typical for the younger 
stems of H. Lomazii (see above, p. 78). 
The point of real interest lies in the leaf-traces, of which two are shown 
` in the section photographed. The inner pair (T. 1) is only just beginning to 
separate from the stele, in the outline of which the two strands (each about 
700 w in tangential diameter) form gentle protrusions, cut off at the back by 
conjunctive tissue. They are quite near together, at an interval of about 
120 p only. This is the earliest stage in the separation of a leat-trace from 
the stele which we have yet met with, and it shows again that the two 
bundles were distinct from their origin. 
The outer trace (T. 2), at a divergence of perhaps ? from the former, is in the 
cortex and consists of two double bundles, about 1150 p apart. The division 
of each of the original strands into two is quite evident, and shows that here, 
as in H. shorense and H. tiliwoides also, the trace ultimately became a 4-stranded 
one. A protrusion of the cortex in the region of the leaf-trace indicates the 
beginning of the base of the leaf. 
In the section previously figured (W. 1304 A), which appears to have been 
* The six transverse sections, in their probable order from below upwards, are: N.19; 
W. 1304 A ; R. 621; S. 444; S. 446; N. 7. 
The longitudinal sections are W. 1304 B and R. 644; the oblique section is W. 1915 P. 
When the joint memoir was written, only the two sections W. 1304 A & B were examined. 
