36 Notes on Recent Literature. 
were protected against excessive loss of water by a hypodermal 
sheath of sclerenchyma and by a thick palisade tissue. The stomata 
were sunk in grooves. The opinion has been expressed that the 
xerophilous characters of the Coal-Measure plants may be the result 
of growth in salt water ; but this would not account for all the facts. 
The occasional alternation of zones of crowded and more widely 
separated leaf-scars on Sigillarian stems may be the expression of 
variation in the rapidity of growth. The absence of regular rings 
of growth in the wood of Lepidodendron and other genera points to 
a uniformity of climate throughout the year. Dr. Gothan has 
recently written a short paper on the absence of annual rings in the 
stems of many Palaeozoic plants and the bearing of this fact on 
questions of climate. 1 Without discussing his remarks on the main 
point, reference may he made to a criticism on the generally 
accepted view, adopted by Bertrand, namely that the occurrence of 
the Glossopteris flora in rocks closely associated with ice-formed 
material necessarily implies that the plants grew in a cold climate. 
He quotes the existence of a Mediterranean flora in the north of 
Italy on glacial moraines of the great ice age as an illustration of 
the falsity of the conclusions as to the Glossopteris flora. But it 
may be asked, is the conformable succession of Permo-Carboniferous 
glacial beds and the plant-bearing strata strictly comparable with 
the unconformable juxtaposition of the Mediterranean flora and the 
deposits of the ice age ? The wide distribution of what has been 
called the boreal flora indicates an absence of climatic zones, and 
the temperature could hardly have been lower than that of our 
summer. The xerophytism of the Carboniferous plants, their rapid 
growth, and the large diameter of the tracheae are regarded by 
Bertrand as evidence in favour of a tropical climate. On the other 
hand, in the southern hemisphere and in India there was extensive 
glaciation at a time when this presumably tropical flora flourished 
in the north. 
The study of the structure of Palaeozoic plants has made 
remarkable strides during the last few decades, but as yet little 
attention has been paid to anatomical data from a physiological or 
ecological standpoint. M. Bertrand’s summary shows what contra¬ 
dictory results may be obtained from a cursory examination of 
anatomical evidence; it should also have the effect of stimulating 
palaeohotanists to pursue a line of inquiry likely to yield interesting 
results and, incidentally, his paper emphasises the need for experi¬ 
mental work on recent plants. A good beginning has been made by 
Mr. Hamshaw Thomas in his investigation of the leaf-structure of 
Catamites which lead him to the conclusion that “ the structure of 
the smaller leaves probably indicates that they grew in a moist 
situation, or where the atmosphere was humid. The larger leaves 
are more xeromorphic in character.” 2 
In the concluding portion of his Presidential Address to the 
Botanical Section of the British Association Meeting at Portsmouth 
this year (1911) Professor Weiss gave an exceedingly interesting 
illustration of the application of data furnished by ecological 
investigations to the biology and ecology of the plants of the Coal 
period. A.C.S. 
1 Die JahresringlosiBeit der palaozoischen Baume und die Bedeu- 
tung dieser Erscheinung fur die Beurteilung des Klimas 
dieser Perioden. Natunviss. Wochenschrift, [N.F.l, Bd. X., 
No. 28, 1911. 
2 On the leaves of Calainites (Calamocladus section). Phil. Trans. 
R. Soc., Vol. 202, p. 51, 1911. 
