tq8 SECTIONAL ADDRESSES 



which reads like an advertisement of a modern patent medicine. It is 

 the dry, white, friable flesh of Polyporus officinalis which grows on larch 

 in subalpine regions ; it has not yet gone completely out of use. 



Similarly, yeast was prescribed medicinally by Hippocrates and later 

 by Dioscorides, and it is still used for various ailments and incorporated 

 in many patent medicines. 



The list of fungi employed as medicines by natives in all parts of the 

 world is very long, and its chief interest lies in the beliefs associated 

 with many well-known species. One of the most celebrated is Cordyceps 

 sinensis, with its attached parasitised caterpillar, which is sold throughout 

 China in bundles tied up with red silk. Captain Kingdon Ward tells 

 me that coolies collect this in the south and east of Tibet and that his 

 own men are always on the look out for it. 



One aspect of the general subject which must be dealt with very 

 summarily is that of mycorrhiza. It will be well to treat of orchid- 

 growing, because there we meet with the best example of a practical 

 application. It has been known for almost a century that fungal hyphse 

 are present in the roots of orchids as they are, as a matter of fact, in those 

 of many other families. Such difficulty was experienced in germinating 

 the minute seeds of orchids that for many years it was thought of sufficient 

 interest to describe and illustrate any seedlings which were obtained. 

 The first practical step which proved of value was that of sowing the 

 seeds on the soil of the pot containing the parent plant, a method 

 apparently introduced by Neumann in 1844. There were modifications 

 of this method, and gradual progress was made, but what success there 

 was could be attributed rather to the ' green thumb ' of the grower 

 than to any essential difference in procedure. At the beginning of the 

 century, Noel Bernard, as a result of his study of Neottia, the bird's nest 

 orchid, realised that the presence of the fungus in the root was in some 

 way connected with the difficulty of obtaining seedlings, and astounded 

 the botanical and horticultural worlds when he extracted the fungus 

 from a root and, sowing seed with it, obtained abundant germination. 

 The method has been used on a commercial basis in France, Germany 

 and this country. 



Following on some experiments by Bernard, L. Knudson has shown 

 that the action of the fungus can be replaced by sugars in the medium. 

 This so-called asymbiotic method has also been employed in commercial 

 orchid growing. Here we have the reverse of what is the common 

 sequence, i.e. a fungus is proved to be necessary to bring about a desired 

 end, and, as a further step, the action of the fungus has been replaced 

 by chemical means. So far as my experience and observation go, the 

 purely chemical method is not so satisfactory as the symbiotic method, 

 though as germination in both is carried out in culture-flasks there seems 

 no theoretical reason why there should be more than a temporary difference 

 in the first stages. It may be added that the first orchid firm to apply 

 the pure-culture method in this country has followed it for a quarter of 

 a century, and for many years germination has been regarded as a routine 

 requiring no scientific supervision. 



Most, if not all, forest trees have mycorrhizal roots, though the relation 



