66 SECTIONAL ADDRESSES 
It is well to elaborate the fact that many of these so-called alge may 
not have been correctly classified. Massive beds of limestone of Permian 
age near Denver, U.S.A., as Prof. Johnson has shown, have a nodular 
character that simulates that of algal limestones, but no trace of algal 
tubes can be found. Even the surface limestones formed as a result of 
capillary action on the borders of deserts may also show banded and 
nodular structure very similar to algal growths, as may be seen in the 
Kalahari desert to-day. 
On the other hand, Sir Douglas Mawson ®° records recent ‘ biscuit ’ 
shapes, and nodular structure, in calcareous deposits forming on coastal 
flats, and beyond any doubt the result of the activity of blue-green algae, 
and yet no minute algz structure can be observed. 
Aside from these possibilities, algee of Cambrian, Ordovician and 
Silurian age of the Solenopora and other types have been determined ; 
and the structures in pre-Cambrian rocks are also probably true alga, 
in some cases ; so that the evidence for a pre-Devonian flora is reasonably 
good. If, and when, fossiliferous terrestrial deposits of these ages are 
discovered, we may obtain some of the higher terms in yet another floral 
series. 
But the flora that has been most thoroughly and extensively explored 
is that of Carboniferous times, and to the late Dr. Kidston of Stirling we 
owe the present accepted subdivisions ; but the work of authors in other 
lands must not be forgotten, for it has had repercussions on the position 
in this country. When I mention Grand’ Eury, Zeiller, Renault, 
P. Bertrand, Potonié, Gothan, Renier, Jongmans, Zalessky, David White, 
I only select a few among the older workers whose influence has been 
felt here. Kidston recognised six divisions in this country in his latest 
memoir.*t 
Radstockian Series 
Staffordian Series 
Westphalian Series (Yorkian Series) 
Lanarkian Series 
Upper Carboniferous Rocks 
{ Carboniferous Limestone Series 
Lower Carboniferous Rocks (Calciferous Sandstone Series. 
As one of these names (Westphalian) has long been used in a wider sense, 
Prof. Watts has suggested the use of the term Yorkian, and this has met 
with general approval. In the past few years the scheme has been 
criticised, especially by mining engineers, as the zoning possible by 
using the florules was not sufficiently close for their purpose. ‘They 
prefer to use marine bands in their work in the Coal Measures. This 
has led to a rather unjust criticism of the use of fossil plants in geological 
work. In any sequence an unusual bed will form a useful datum line, 
if it be sufficiently extensive. In a marine series an algal phase is extra- 
ordinarily important, as Prof. Garwood has shown ; *? and a marine phase 
SURO R/EG OP ANG leg liceKy, LOZ, 
31 Fossil Plants of the Carboniferous Rocks of Great Britain, 1923-25. 
32.9,].G.S., 1912 ; Geol. Mag., 1914; et alia. 
