YHE AUSTRALIAN NATURALIST. 197 
‘ditions are unfavourable for the bacterial action rendering the 
humus available, the saprophytic mycorhizae take their place 
Mycorhizae may be useful in three ways to the host plants, 
and thus indirectly to themselves. 
I. Organic and mineral matter may be rendered available. 
2. Roots no longer possessing root hairs, may be able to 
-absorb water through the fungus hyphae. Mycotropic plants 
-are normally poorly supplied with roothairs. 
3. Atmospheric nitrogen may be assimilated through the 
fungus as in the case of Psewdomonas in the legumes. This 
fixation of free nitrogen has been shown in the case of Podo- 
-carpus, and claimed in regard to certain heaths. Where the 
fungi have been isolated and determined, they have proved to 
be species of Phoma.  Ternetz has shown that three of five 
‘Species isolated from certain heaths (Hricaceae) have a de- 
cided capacity for nitrogen fixation in cultures. 
‘That this applies generally to Mycorhizae has still to be 
proved. It would certainly indicate a similarity of associa- 
tion to that of the legumes and bacteria. Whatever its value, 
it seems certain that the mycotrophic condition to greater or- 
‘less degree is common in Australia. Probably it is asso- 
ciated with the drought conditions periodically experi- 
-enced and possibly to the rather low nitrogen content of 
our soils. ; 
The study of such associations as these makes us realize 
again the remarkable complexity of Nature’s methods, and 
-the danger that lies in arbitrary divisions too closely applied. 
Who can draw the line between parasites, saprophytes, and 
normal terrestial plants? : 
Native plants found by C. T. Musson to have mycorhizae 
~on their roots. 
Hibbertia, sp. Dilleniaceae. 
Sida rhombifolia, Malvaceae. 
Oxylobium trilobatum, ~ Leguminosae. 
Pultenaea flexilis, Leguminosae. 
Gastrolobium. grandiflorum, Leguminosae. 
Kennedya rubicunda, Leguminosae. 
Acacia linifolia, Leguminosae. 
Lucalyptus sp., a Myrtaceae. 
Helichrysum lucidum, Compositae. 
Panaz sambuctfolius, Araliaceae. 
Goodenia ovata, Goodeniaceae. 
Epacris, sp., Epacrideae. 
Myrsine variabilis, Myrsinaceae. 
Lyonsia lilacina, Apocyneae. | 
Erythraca australis, Gentianeae. 
