76 SECTIONAL ADDRESSES 
the southern hemisphere. How far this is the result of inadequate 
collections or inaccurate determinations is difficult to ascertain. 
Fossit PLANTS AND SPECIAL ROCK-TYPES. 
It is not my purpose to discuss the origin of coal, oil-shale, ironstone, 
limestone, etc., that are the result of the accumulation of plant debris or a 
consequence of the activity of plant life in the past, but a recent publi- 
cation by Murray Stuart makes such a direct correlation of definite fossil 
types with oil formation in Burma that some comment is merited. ‘The 
fossil wood first described by La Hire in 1692 consists chiefly of pieces of 
Dipterocarpus stems, and the living D. turbinatus is the source of the 
Garjan oil of commerce, a single tree yielding, on occasion, 40 gallons of 
oil per annum.*® Murray Stuart *® suggests that the petrifaction of the 
trees now found in the Irrawaddi Series released the oil now accumulated 
in the underlying Pegu Series. The theory of the origin of oil from 
vegetable material is no new one, but such a direct relationship has never 
before, I think, been suggested, nor can it be accepted without further 
investigation. 
FossiL PLANTS AND CLIMATE. 
On account of the clearly marked zonal distribution of plants to-day, 
it has long been held that they should be good indexes of climatic zones 
in past time. The position in this regard is not so definite as was formerly 
maintained, when the continents and oceans were held to be fairly perma- 
nent in position, though not necessarily in size or shape. Migrations of 
plants were considered to be effected slowly and in consonance with 
climatic changes. ‘This was especially so in relation to the Tertiary 
flora and to the Ice Age. But the discovery of many floras in Arctic and 
Antarctic areas, and several Ice Ages, has compelled re-consideration of 
the whole position. The other discovery, that oceans and continents 
had probably not occupied the same relative position with respect to the 
poles as they do to-day, further complicated matters. 
In a recent discussion at the Royal Society °° Prof. Seward put the case 
from the botanical point of view and stated that plants have been over- 
estimated as indexes of climate. As regards the older floras, he stated that 
the plants were of little value, because they were extinct. One of the 
arguments that used to be advanced for a tropical climate during the 
accumulation of the Coal Measures in England was the large size of some 
of the specimens. Last autumn I had the opportunity, through the good 
offices of Prof. Fearnsides, to examine and photograph probably the 
largest Carboniferous plants ever seen. They were casts of the stems 
of members of the Lycopodiales, and their stools ranged up to 6 ft. 3 in. 
in diameter, or 20 ft. in circumference. Slightly smaller specimens in 
the same vicinity had been described by Sorby © and are still protected by 
wooden huts erected round them. Now members of this relatively lowly — 
plant group reaching the enormous size of forest trees must, according 
48 Watt, Dictionary of Economic Products of India, vol. iii., p. 164. 
49 Inst. Pet. Tech., 1925, p. 296: Geology of Oil, etc., 1926. 
50 “ Discussion on Geological Climates,’ Pyoc. Roy. Soc., ser. B, vol. 106, 1930. 
BONE Gr: Sol O7ls 
