August, 1941 The Queensland Naturalist 3.23 
endotrophic or internal type of mycorliiza such as occurs 
in Hoop pine. 
Hartig and other botanists considered that the fungi 
on the roots were injurious parasites, but by 1900 he and 
others had modified their view. Even in modern times 
several people continue, without support, to consider the 
fungi as being in general harmful. 
In 1900 Stahl advanced a theory to explain my co- 
trophy. This is his famous mineral salt theory. He con- 
sidered that the fungi connected with the tree roots, by 
reason of their wide distribution in the soil acted as very 
efficient root hairs, and were able to supply the trees with 
mineral salts obtained from the soil in return for carbo- 
rydrates which were considered to be obtained from the 
tree. 
Frank and others thought that the fungi supplied 
organic nitrogen to the trees as their main function besides 
acting as a means of transport for other soil nutrients. 
In Sweden, Melin showed (1925) that not only were 
the fungi beneficial to the trees which he studied, but in 
most cases were absolutely essential for vigorous growth. 
He and others have carried out a considerable amount of 
research which has shown that particular fungi only occur 
in association with certain genera of trees with which they 
form mycorhizas. He also disproved the idea that the 
mycorhizal fungi can fix atmospheric nitrogen which they 
were previously thought by some botanists to supply to 
the trees. 
Melin demonstrated that in soils where no mycorhizal 
fungus existed trees always died unless an appropriate 
fungus was introduced. This was important in reforest 
ing treeless country such as the heaths and moors. 
Following all this investigation it has become estab- 
lished that the failure in growth of seedlings in many 
forest nurseries has been due to the absence of the re- 
quisite fungi in the soil, and with the introduction of fungi 
good results have been achieved. An illustration of this is 
in the Philippine Islands where the Benguet pine (Finns 
insularis) which occurs on the highlands could not be 
grown on the coastal lowlands until soil containing the 
mycorhizal fungus was carted from the hills and scattered 
over the nurseries on the lowlands when good growth was 
obtained. Another example is the case of Queensland 
Hoop Pine (Araucaria cunninghamii) in Nyasaland. 
There, no growth could be obtained until the nurseries 
