FEBRUARY, 1918.] THE ORCHID REVIEW. 2) 
NES) ROOT-FUNGI OF ORC KS 
x : HIDS. 
BP) ORC 
N esteemed correspondent, who expresses his appreciation of the article 
on the Root-Fungi of Orchids (pp. 4-7), asks: Can you give us the 
practical side of the question? How is the fungus taken from the roots ? 
How and upon what medium is it cultivated? Lastly, how is it then used 
in relation to seeds which one wishes to sow ? 
The following method of cultivation adopted by Dr. Hans Burgeff has 
been summarised for us by Miss E. M. Wakefield, who recently gave a 
paper on the subject before the Kew Gardeners’ Mutual Improvement 
Society. It may seem a little complex, but the necessity of adopting what 
may be termed laboratory methods is due to the fact that without such 
control one is just as likely to obtain a crop of moulds that are useless for 
the purpose, or even injurious. The essential points are, to prepare a 
sterilised nutrient medium on which.to grow the fungi; to secure the right 
kinds, while excluding others, and then to introduce aseptically the seeds of 
the Orchid which it is desired to germinate. Some knowledge of laboratory 
technique is necessary. The first point is to procure the necessary 
apparatus and to prepare the nutrient medium on which the fungi are to 
be grown. 
Noel Bernard used a medium consisting of gelatine with about five per 
cent. Salep. Hans Burgeff found, however, that the following nutrient 
medium was preferable. It contains all the mineral salts necessary for the 
nutrition of both fungus and Orchid seedling : — 
Dihydrogen potassium ssaings oe .. I gramme 
Calcium chloride __... as fe OT re 
Sodium chloride sae ee i i ‘sy 
Magnesium sulphate... Sue ibe O83 i 
Iron chloride ... yee bs hs pa Or. 
Ammonium chloride .. o°5 
These quantities are Slacaived in 1,000 grammes of distilled water or 
(better still) pure rain water. To make a firm medium, Agar-agar is added 
to this solution in the proportion of 1°5 gr. Agar-agar to 100 cubic 
centimetres of the solution. The Agar-agar is soaked for about twenty-four 
hours in the solution, and then dissolved by heating, after which is added a 
trace of starch (rice or potato) mixed with a little cold water. The mixture 
is neutralised with sodium-carbonate until it gives a faint blue reaction with 
litmus paper. It must be filtered while hot, and is then poured into tubes 
(the mouths of which are closed with cotton-wool) and sterilised at 100° C. 
(the boiling point of water) for } to 2 hours on three successive days. After 
sterilisation the medium may be poured into sterilised Petri-dishes, or left 
