20 BOTANICAL GAZETTE [JANUARY 
today, that for the germination of orchid seeds infection of the 
embryo by the appropriate fungus is essential? BERNARD believed 
that the action of the fungus was a physicochemical one, in that 
the fungus would cause an increase in a concentration of the cell 
sap, which increase in concentration would induce germination and 
the formation of a protocorm in somewhat the same way that the 
form of algae could change by increasing the concentration of the 
external solution. He points out that the fungus can invert — 
sucrose and this may occur in the embryo. 
The writer believes that the fungus may bring about germina- 
tion in another way. As previously pointed out, in all his media 
BERNARD used a substance known as salep. This is a powder 
derived by grinding the dried tubers of certain species of orchids, ) 
and is rich in pentosans and starch, containing also about 5 per 
cent of organic nitrogenous substances. It probably contains 
some soluble organic and inorganic matter, judging from freezing- 
point determinations made by BERNARD. In view of the fact 
that organic matter is present, it is conceivable that the influence 
of the fungus might be to digest some of the starch, pentosans, 
and nitrogenous substances; which digestion products, together — 
with secretions from the fungus or products produced on decomposi- 
tion of the fungus, might be the cause of germination. In brief, it 
is conceivable that germination is induced not by any action of 
the fungus within the embryo, but by products produced externally 
on digestion or secreted by the fungus. Unfortunately I have not 
as yet succeeded in satisfactorily isolating the organism stated as 
necessary by BERNARD, nor has it been possible to purchase salep. 
Work is still in progress on this problem. There are, however, — 
certain facts which support the idea that the action of the fungus 
is not necessarily internal. BERNARD does not give any analyses — 
of the medium used, but he does give certain cryoscopic data. 
The medium generally used, made with salep, had a freezing-point 
depression of 0.o1° C. Assuming that this depression (A) is pro- 
duced largely by hexose sugars, it would indicate at the outset of the 
experiment a concentration of hexose sugars equivalent to 0.1 per 
cent glucose. It isnot possible, of course, to say that thisdepression 
is due entirely to hexose sugars; perhaps other sugars are present, — 
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