as become increasingly difficult.

For Cypripediums, and especially Selenipediums, a proportion of good,
fibrous loam should be added to the compost recommended for epiphytal
Orchids, the proportion of loam being increased as the plants get
larger. Phaius, Calanthes, Zygopetalums, Zygocolax, and other plants of
a similar character should also have a proportion of loam-fibre in the
compost, and in these cases Orchid peat may be substituted for Osmunda
fibre, if it is of good quality. So far as it has been tested, Osmunda
fibre has an advantage over other fibres, in that it is more durable,
retaining its fibre intact longer than any other. Osmunda fibre and
Polypodium fibre in equal proportions, with an addition of leaves and
Sphagnum-moss, make an excellent material for all young, epiphytal
Orchids, the finer Polypodium fibre, if well worked in, giving substance
to the more open Osmunda fibre.

For very small plants it is well to rub the mixture through a coarse
sieve, but after the early stages the use of the sieve should be
discontinued, and the compost carefully mixed with the hands.

CHAPTER XX

ENUMERATION OF THE PRINCIPAL GENERA AND SPECIES IN CULTIVATION

~Acanthophippium.~--A small genus of terrestrial plants with oblong
pseudo-bulbs, and broad, plicate leaves. Scape erect, flowers
ventricose, yellow and reddish-purple. Warm house. Pot in equal parts of
turfy loam, peat, and leaves. Rest dry after the leaves fade and growth
is completed. The most familiar species are _A. bicolor_, _A.
javanicum_, and _A. striatum_.

~Acineta.~--The species of Acineta are epiphytal Orchids with stout
pseudo-bulbs and broad, coriaceous leaves. The flowers are produced in
pendulous racemes; they are fleshy, whitish, or yellow, and spotted
with purple or brown. They should be grown in baskets suspended in the
intermediate house. _A. Barkeri_, _A. densa_, and _A. Humboldtii_ are
free-growing species.

~Acropera.~ _See_ ~Gongora~.

~Ada.~--Cool-house genus from Colombia. Leafy evergreen plants with
racemes of orange-scarlet flowers. _Ada aurantiaca_ is almost the sole
representative of the genus in gardens, and should be grown even in the
smallest collections.

~Aeranthus.~ _See_ ~Angraecum~.

~Aerides.~--A large genus of evergreen Orchids with distichously arranged,
leathery, green leaves, the stem producing air-roots freely. Natives of
India, the Malay Archipelago, and other parts of that region, extending
to Jap