THE ORCHID REVIEIWV. 345 
time, it soon reappears if the conditions remain unchanged. This spot is 
undoubtedly caused by a too stagnant atmosphere, as it never occurs when 
a structure is sufficiently ventilated. Beware, then, at this season, for 
during the autumn, and sometimes even in winter, periods of exceedingly 
damp, and, at the same time, very mild weather occur, and at such times 
the doors and ventilators, both top and bottom, should be opened wide, and 
if the side lights directly opposite the plants are constructed so as to admit 
of it, they should be partly opened too. 
This is the time for foggy weather. The pure fogs of the country are in 
no way injurious, but those in the neighbourhood of large towns are so 
charged with smoke and various chemical fumes, which are unable to pass 
away, that vegetation is seriously handicapped. Under these circumstances 
it is not at all surprising that when this modern giant swoops down upon 
our plants, the flowers and flower-spikes are stricken, and even the foliage 
of some species is likewise affected, more especially if very dry at the root, 
or the atmosphere of the house very much parched. My experience is that 
plants which are moist at the time of a heavy fog do not suffer so much as 
those that are very dry, and therefore I would recommend that drought 
should be guarded against at such times, that the ventilators be closed, and 
sufficient warmth maintained to cause a genial temperature. Time per- 
mitting, it is an excellent plan to sponge the leaves of Orchids with clear 
soft water when the fog has passed away. 
Damping-down in all departments will now require to be done once or twice 
a day, in accordance with the outside conditions. Should the weather be damp 
and mild, once will suffice, and that during the morning; but should the 
weather be such as to necessitate a good amount of fire heat, twice a day 
will probably not be too much; though here again we must be guided by 
circumstances. 
I have previously recommended the ordinary open greenhouse stage for 
Orchid houses, so that the air can freely circulate up between the plants, in 
preference to closed stages with moisture-retaining material, such as shingle, 
or shell-gravel placed on them, though in the former case damping between 
the pots is more frequently needed than in the latter. Then again the 
floor of one house may be composed of some hard material, such as concrete, 
in another it may be ashes, or something in the nature of ordinary soil. 
The latter kind of floor in my opinion is better generally than the former, as 
the moisture arising therefrom is more regular and better for the plants. 
Cattleyas and Dendrobiums have perhaps been the most affected by the 
small amount of sunshine this year. Cattleyas are late, some in the forma- 
tion of their pseudobulbs and others in flowering, and all require more 
artificial warmth than is usual at this season. This will assist them to 
some extent in maturing: artificial heat can never quite make up -for 
deficiency of sun heat. 
