a8 + THE ORCHID REVIEW. [Jan.-FEB., 1919. 
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bs. POTTING FIBRE FOR ORCHIDS. DS 
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HE difficulty of obtaining suitable potting fibres for Orchids during the 
war has Jed to the use of various substitutes, which, judging from — 
letters received, have not always proved satisfactory, and a question has 
arisen as to what some of them ate. _ Some time ago we received a sample 
‘of the fibre known as Ar, with an enquiry as to its origin, and so far as we 
could make out it was the roots of what is known as the male fern, Lastrea 
(or Nephrodium) Filix.mas. A sample from another source was not identical, 
and appeared to be a mixture, while one now received appears again to be 
Lastrea. The present scarcity of potting fibre may partly account for this 
want of uniformity, and it invites a discussion as to potting fibres in general. 
_ The basis of the old compost for epiphytic Orchids was what is 
commonly known as good fibrous peat, and the best Orchid peat we believe 
consists chiefly of bracken root (Pteris aquilina), this being chopped or 
pulled to pieces, so as to exclude the finer particles of soil which adhere to 
the roots and render it too close ér too retentive of moisture. Then 
polypodium fibre, the roots of Polypodium vulgare, came into use, and is 
still much appreciated for certain Orchids, and this was followed by 
osmunda fibre, the roots of one or more North American species of 
Osmunda, probably unsurpassed for the Cattleya group—when obtainable, 
_ and the sources of supply may soon be open again. Lastly came into use 
what is known as Ar fibre, which was by some considered to be a proprie- 
tary article, though we are told that such is not the case. 
It thus appears that the basis of the compost used for epiphytic Orchids 
is some kind of fern fibre, and we have been told that it matters little what 
it is so long as it is clean and porous, and not liable to become water-logged 
or sour. Other substitutes have been tried, among the most recent of 
which is sponge trimmings, which Mr. Watson now admits has not proved 
the success that he anticipated, as, with the exception of Cypripediums, 
nourishment epiphytic Orchids naturally get.” 
g nt matters in solution for its support. 
less it can obtain the necessary nutrient 
matters from the compost. Herein lies the use of a compost. By its 
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