-soil)
may be used in the compost with advantage. Scarcity of good Orchid peat
brought about the introduction of Polypodium fibre and Osmunda fibre,
both excellent materials when prepared as recommended in the chapters on
Potting Epiphytal Orchids, and Hybrid Orchids. For the general repotting
of those requiring it September is the best month, but in early spring
the plants should be examined in order to repot those which need
immediate attention. The Odontoglossum house must be kept cool at all
seasons, and the necessity to have lower night temperatures must be
strictly recognised. Free ventilation should be provided, but at all
seasons when drying, east winds prevail, especially in winter and early
spring, the bottom ventilators should be only opened slightly, the top
ones being kept closed; the laps of the glass of the roof will admit
sufficient air. Moisture should be freely distributed about the house by
syringing beneath the staging and between the pots in summer, but in
winter the houses, if kept at the prescribed low temperature, will be
moist without much water being distributed. _Odontoglossum citrosmum_,
_O. Rossii_, _O. membranaceum_, and some other Mexican species should be
grown in baskets or pans; _O. coronarium_ and its varieties in oblong
baskets; _O. Londesboroughianum_ on rafts. Odontoglossums require
abundance of water, but are easily injured if allowed to get soddened.
Water should therefore be given systematically--a thorough watering, and
no more until the effect of it is passing and the still moist material
is sufficiently near the dry point. After flowering, a lessened supply
should also be given for a time, but the plants must not be dried off.
At this stage it is a good time to repot any requiring to be repotted.
In the cool houses, and indeed all the Orchid houses, observation should
be made as to the rapidity of evaporation of water from the floors and
staging. If the moisture evaporates too quickly and the floors and
stages become dry rapidly, it must be remembered that the conditions are
not favourable to sustaining the vitality of the plants in the house,
for, where rapid evaporation takes place, a similar process affects the
tissues of the plants. Means should be taken, either by lowering the
temperature or checking the ventilation, to sustain a lasting humidity
in the houses.

~Oncidium.~--This is a large genus, most of the members being suitable for
cultivation in the intermediate hous