TRAY M wae Y EE T TEE E Y. N 
OF THE BRITISH COAL MEASURES. 61 
HETERANGIUM SHORENSE, sp. nov. 
The one specimen on whieh this species is based was discovered by 
Mr. Lomax and his son on August 12, 1912, in material from Shore, Little- 
borough. The fragment was 1°5 inches (3:75 cm.) long, and a series of 
15 transverse sections was cut (now numbered 2781-2795 in my collection). 
It is a fine stem, 17-18 mm. in diameter, the wood of the stele, though 
almost without secondary thickening, reaching 7 mm. in diameter (Pl. 1. 
Phot. 1; Pl. 3. fig. 1). The general outline of the stem is approximately 
cireular, with more or less marked prominences where a leaf-base is met with. 
The cortex is for the most part well preserved; it is 3-4 mm. thick. A 
considerable part of the pericycle is also preserved, often in contact with 
the inner edge of the cortex. The phloem has almost wholly perished ; the 
gap between pericycle and wood was no doubt caused partly by shrinkage 
and partly by actual destruction of tissue. 
Stele. 
We will at first confine our attention to the wood, which in three of the 
sections is almost or quite complete (Pl. 1. Phot. 1; P1.3. fig. 1). The great 
feature of the primary xylem (and little else is present) is the grouping of 
the tracheides in a large number of definite packets, separated by a narrow 
reticulum of conjunctive parenchyma. ‘The tracheal packets commonly 
contain from 6-15 elements each, and range from about 400 to 650 w in 
diameter. In the middle part of the wood they are fairly isodiametric, while 
towards the periphery they become lengthened in the radial direction. "These 
peripheral groups are very distinct, as is usual in the Coal-Measure species. 
The deep clefts between them, seen in some places, are merely due to 
shrinkage. The surface of the wood is somewhat ribbed, the peripheral 
groups being convex (fig. 1). 
The parenchymatous reticulum between the tracheal packets appears 
narrower than it should be, owing to a partial collapse of the cells. 
The tracheides of the metaxylem are generally of large size; there is, 
of course, much variety, but we may take 200 pu as an approximate mean 
diameter. "Towards the outside, i. e. in the neighbourhood of the protoxylem 
of the peripheral strands, the tracheides become rapidly smailer, down to 25 u 
or 20 p. The preservation is such that it is not, as a rule, easy to determine 
the position of the actual protoxylem. Where this can be fixed it is found 
near the outside, separated by from two to four small elements from the outer 
edge of the wood (P1.3. fig. 5). The question may still arise whether all these 
centrifugal xylem-elements were really primary, for a certain amount of 
secondary growth had taken place—at least locally. On one side of the stele 
there are a few irregular layers of radially arranged tracheides—at most five 
in a radial row (fig. 6). These secondary elements are little larger than the 
smallest primary tracheides—about 25-35 u in diameter. On other parts of 
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