ee may COE Pye Vor, EIRE UU T ER 
" i 
90 DR. D. H. SCOTT ON THE HETERANGIUMS 
Sclerotic tissue present both in pericycle and cortex ; the sclerotic nests 
in the cortex forming massive blocks, sometimes (in stems of the « form) 
developed to a remarkable extent. 
Leaf-trace consisting of two bundles where it leaves the stele, the 
constituent bundles often very widely separated in the cortex, when 
adventitious roots pass out between them.  Trace-bundles without secondary 
wood of their own. The double trace beginning to divide into four as it 
enters the leaf-base. Four bundles, sometimes further subdividing, in the 
petiole. 
Number of traces in the transverse section, one only in some specimens, 
two or perhaps more in others. Traces traversing the stem for a long 
distance before passing out. 
Stem observed to branch, the secondary growth in this case starting at the 
base of the branch. 
Details of cortical structure and of arrangement of leaf-traces varying in 
different forms of stem. 
Locality. Dulesgate, Lancashire: Lower Coal Measures. 
All the specimens, apparently from a single nodule, discovered by 
Mr. James Lomax about 1890. 
It may be mentioned that the present re-investigation has thrown no new 
light on the structure of the root in Heterangium Lomax. That question 
remains now as it was in 1895 *. 
HETERANGIUM MINIMUM, sp. nov. 
A single specimen of this small stem occurs in a block from Dulesgate, 
of which sections were received from Mr. James Lomax in February, 1903 f. 
Though the locality is the same as that of H. Lomazii, the material is quite 
different, and contains different plants. There is therefore no presumption 
of specitic identity between this form and those referred to H. Lomaxii. The 
characters indicate that it is distinct. 
The dimensions of the stem, about 2:9 mm. by 1:7 mm. in its somewhat 
crushed condition, are unusually small for a Heterangium. The best section is 
shown in Pl. 4. fig. 19. The wood, including a few secondary layers, measures 
about l-6x 1 mm. The primary wood consists mainly of tracheides, with 
comparatively little conjunctive parenchyma. The peripheral xylem-strands 
are not sharply defined, and the principal rays of the secondary wood by no 
means conspicuous. In these respects the specimen recalls H. Grievit rather 
than the Coal-Measure species. The tracheides of the metaxylem are decidedly 
large for the size of the stem, often exceeding 150 p in diameter. The 
structure of the peripheral strands is mesarch, with one or two layers of 
centrifugal primary wood. The secondary wood, which reaches a maximum 
* Williamson & Scott, 1895, pp. 758, 764. The evidence there brought forward relates 
entirely to the Dulesgate species, H. Lomarti 
t The sections are S. 1801, 1803, 1804, 1805, and 1813, all transverse. 
