“14 BOTANICAL GAZETTE [yoLy 
NOTES FOR STUDENTS. 
KoeERNICKE finds that Roentgen rays, after first accelerating growth for a 
brief period, as do many injurious agents, later retard it? Experiments with 
radium bromid3 inclosed in glass, so that only the 8 and 7 rays acted (@ rays 
and the gaseous emanation being stopped by the glass), showed a strong retarda- 
tion of the growth of seedlings, but no fatal injury. Somewhat similar inhibition 
of growth occurred with certain fungi after prolonged action of the rays.—C. R. B 
Harvey‘ has made a study of the physiographic ecology of Mount Ktaadn, 
tracing the origin and development of the flora and noting the various factors 
operative in determining the present plant physiognomy. He also shows that 
the accepted goer ie of physiographic ecology hold in general in alpine as well 
as in lowland regio The associations discussed are the crustaceous lichens, 
the reindeer moss, se alpine-tundra, the ‘‘Krummholz,” the Picea-Abies forest, 
the “roches moutonnées,” the pioneer stage of the alpestrine meadows, the 
meadow stage, the shrub stage, ponds, and sphagnum bogs.—J. M. C 
BoopieEs has made an experimental study of the ecological anatomy of the 
leaves of Pteris. Leaves grown in dry and exposed situations are xerophytic 
and have a “hypoderm;”’ while those sheltered and shaded are of the “shade- 
leaf” type, having no hypoderm and either weakly developed or no palisade 
tissue. The same differences were developed by different leaves of the same 
plant, and by different parts of the same leaf. A plant grown first in a damp 
greenhouse and then in the garden produced shade-leaves in the former and 
sun-leaves in the latter. It was further noted that the mature type of structure 
is not determined at an early stage in the growth of the leaf —J. M. C 
SEWARD® considers the Carboniferous, Rhaetic, and Wealden floras of 
South Africa in an important paper. The Ecca beds are held to correspond in 
a general way with the Upper Carboniferous of the northern hemisphere, and 
are more definitely correlated with the Karharbdri beds of the Lower Gondwana 
in India. Evidence from the contained plants emphasizes the well-known simi- 
larity which existed during the Carboniferous between the floras of India, South 
? KOERNICKE, Max, Ueber die Wirkung von Réntgenstrahlen auf die Keimung 
und das Wachsthum. Ber. Deutsch. Bot. Gesells. 22: 148-155. 1904. 
3 KOERNICKE, Max, Die Wirkung der Raditenstrahien auf die Keimung und 
das Wachsthum. ibid. 155-166. pl. 10. 1904 
a 4 Harvey, Le Roy Harris, A study of the physiographic ecology of Mount 
taadn, Maine. The University of Maine Studies, no. 5- pp. 50. figs. 6. Dec. i 
. 5 Boopte, L. A., The structure of the leaves of the bracken (Pteris aquilina 
Linn.). Jour. Linn. Se. Bot. 35:659-669. 1904. 
ARD, A. C., Fossil floras of Cape Colony. Ann. S. African Museum ~ 
1-116. ey ie. fies. 8. 1903 
