124 
August, 1941 
The Queensland Naturalist 
were inoculated with soil from beneath an old big tree 
growing in a park. In Australia similar phenomena have 
occurred with exotic pines such as Pinus radiata, P . taeda, 
etc. The establishment of the shelter belt of trees in the 
great plains of America has also brought up similar 
problems. 
Orchids also are mycotrophic. In their case the 
mycorhiza is of the endotrophic (internal) type. The seed 
of the orchid will not germinate naturally unless in con- 
tact with an appropriate fungus. The fungus in the orchid 
root conveys to the orchid the breakdown products of the 
bark or soil organic matter on or in which the plant lives. 
By rotting the organic matter the fungus obtains sugars 
and other nutrients which it supplies to the plant. 
The place of the fungus in the seed germination of 
orchids can now be taken by nutrient media rich in sugars, 
etc., and on which the seed will germinate and the seedling 
grow. This method is in general use for the production of 
orchids and orchid hybrids by nurserymen. Before the 
discovery of the necessity for the presence of the fungus 
it was only by chance that any seedling orchids could be 
raised artifiicially as is the case in nature. 
The growth of orchids which have no green leaves, 
such as our native potato orchid, Galeola cassythoides, and 
are therefore unable to manufacture sugars for themselves 
by the aid of sunlight, is explained by the presence of the 
mycorhizal fungi which supply these substances to the 
plants as breakdown products of rotting vegetation. 
A number of unhealthy features in tree growth have 
now been traced to the state of the mycorhizal system of a 
tree. One of these, 4 'fused needle disease” of species of 
Pine is found in various parts of the world, including Eng- 
land, the United States, New Zealand and Australia. In 
Queensland this trouble gave considerable cause for anxiety 
for some time and was therefore investigated. It was 
found to be a mycorhizal trouble. Experiments showed 
that the continual addition of fresh organic matter cured 
the disease. Later, fertilizer experiments showed that the 
application of phosphatie manures was able to do the same 
thing more satisfactorily. It was found that the applica- 
tion of phosphates manured the undergrowth in pine plan- 
tations on poor soils, thus causing a greater development of 
weeds, etc., which contributed their quota of dead leaves, 
etc., to the soil surface. This leaf litter was also of richer 
composition due to the fertilizer. The mycorhizal fungus 
