354 Notes and Comments. 
was asked to advise whether there was any geological basis for 
such an opinion, and he frankly told the section that he re- 
ported that, so far as he knew, there was no warrant for the 
opinion at all. He saw now from Professor Wallace’s obser- 
vations on the Manitoba boulders that it was quite possible 
and probable that such a difference might exist in favour of 
the Norwegian granite. The Canadian speaker had shown that 
the durability of the granite depended upon whether it contained 
soda or potash in its felspar. The potash felspars were strongly 
acted upon by salt water—not by the salt solution directly, 
but by an acid solution which arose indirectly from the brine. 
The soda felspars were not readily affected. It remains to be 
proved whether the Norwegian granite contains felspars con- 
taining potash or soda, if they contain soda, then it is quite 
probable that the rule-of-thumb experience of the engineers 
was right. 
THE HETERANGIUMS OF THE BRITISH COAL MEASURES. 
Dr. D. H. Scott stated that Williamson, in his published 
papers, only recognised two British species of Heterangium, H. 
Grievit and H. tiliwotdes. Under the former name he included 
not only the Lower Carboniferous plant from Burntisland, on 
which the species was founded, but also certain Coal Measure 
forms from Dulesgate. In the joint work by Williamson and 
the present author the same nomenclature was adopted, but 
a second form from Dulesgate was also described under the 
provisional name H. cylindricum. H. tiliwoides, a Coal Measure 
species from Halifax, remarkable for the great development and 
perfect preservation of the phloem, has been kept distinct ever 
since its first discovery in 1886. The enormous difference 
of age between the Burntisland and the Dulesgate plants 
rendered their specific identity highly improbable, and the 
latter has been separated under the name H. Lomaxit, origin- 
ally suggested by Williamson himself, after the name of the 
discoverer, though not published. 
HETERANGIUM LOMAXII. 
H. Lomaxii is characterised by the great distinctness of the 
primary xylem-strands, by their nearly exarch structure, with 
little primary centrifugal wood, by the abundant secretory 
sacs of the stele and by the rather scattered leaves. In the 
Dulesgate material, several forms of Heterangium stem have 
been found in association ; it is unlikely that they are specific- 
ally distinct—they more probably represent axes of different 
orders. The provisional species H. cylindricum differs in no 
important respect from H. Lomaxii, to which it should be 
reduced. A very fine Heterangium from Shore was dis- 
covered by Mr. Lomax and his son in 1912. It is of large size, 
at least 17 mm. in diameter, though without secondary growth. 
Naturalist, 
