Some Observations on Isoetes Drutnmondii, A.Br. 
BY 
T. G. B. OSBORN, D.Sc., 
Professor of Botany in the University of Adelaide. 
With fifteen Figures in the Text. 
/ . SOETES DR UMMONDII is a small terrestrial species that has been 
recorded in West Australia and Victoria. It has recently been found 
in several localities in South Australia, always growing in soil that is wet 
in the rainy season, though not submerged, and baked dry in summer. 
The presence near Adelaide of a ! h abundance of material of an Isoetes 
having a subterranean stock has afforded an opportunity to make observa- 
tions in the field on certain points in the biological morphology of the plant 
and to study its method of spore dispersal. 
The material has all been collected in South Australia, chiefly at 
Belair, near Adelaide, where the majority of the field observations were 
made. Much of the laboratory work was carried out in the Botanical 
Department, University of Adelaide, but it has been completed in the 
Cryptogamic Research Laboratory, University of Manchester, whilst 
holding an Honorary Research Fellowship of the University. My thanks 
are due to Prof. W. H. Lang, F.R.S., for facilities afforded me in his 
laboratory, for the generous way in which he has placed material of other 
species at my disposal for comparison, for his kind interest, and for helpful 
criticism. 
Field Observations. 
# 
The conditions under which Isoetes Dr'itmmondii grows have been 
described recently ; 1 it is sufficient to recall here that in South Australia 
it occurs in a region of winter rainfall ; ^8o per cent, of the total annual 
precipitation (which is about 29 in. at Belair) falls in the seven months 
April to October inclusive. During this period the weather is cool, and 
the light intensity is frequently diminished by cloud or mist (though there 
are many intervals of bright sunlight) and the soil is often saturated. In 
October the temperatures become higher, and the rainfall usually diminishes 
1 Osborn, T. G. B. : Trans. Roy. Soc., S. Aus., vol. xlii, pp. 1-12, 1918. 
[Annals of Botany, Vol. XXXVI. No. CXLI. January, 1922.] 
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