JaN.-FEB., ty19"] THE ORCHID REVIEW. 19 
gradual decay it gives up the nécessary food substances, until exhausted or 
until it becomes sour or sodden so that the roots perish, and can no longer 
carry on their proper functions. The water may, and often does, contain 
the necessary nutrient matters in a state of solution, hence the virtue of 
rain water, or of such additions to the water used as that known as the 
“Cookson formula.” The use of manure for Orchids has been recommended, 
but as often deprecated because of its injurious effect upon the roots. Mr. 
Burberry always strongly deprecated the use of manures, but even he 
advised the addition of a spadeful of something to the tank if the water was 
not right; and that spadeful of something is what all Orchid growers who 
are not satisfied with their results are in search of. * 
Both the mechanical and nutrient qualities of the compost need consider- 
ation, hence the importance of the substances that’are added to the fibre ; 
also of efficient drainage. Crocks and sand are used to keep the compost 
open, and sphagnum moss, while partly serving a similar purpose, is very 
retentive of moisture. Leaf mould, dried cow manure, and loam, when 
added, are nutrient matters, and must be added in such a way as not to 
affect detrimentally the mechanical properties of the compost. The addi- 
tion of loam or leaf mould, or both, is important in the case of many 
terrestrial Orchids, because it is their natural medium. 
Orchids generally may be regarded as humus lovers, and in the case of 
epiphytes its presence in the necessary quantity and condition is all that is 
essential, due regard being paid to the water supply in accordance with the 
nature of the plant, its stage of growth, and the season ofthe year. Many of 
the popular Orchids in cultivation may be described as pseudo-epiphytes, 
that is to say they grow in accumulations of humus on the branches of the 
trees, and thus are best grown in pots. Others have true aérial roots, 
which in a state of nature wander along and round the branches, adhering 
tightly to the bark. In both cases the twigs and branches of the trees may 
be regarded as the collecting ground of the water which is continually 
trickling past the roots, which are thus able to obtain the necessary food 
supply from the various salts held in solution. They have become adapted 
to their surroundings ; they grow during the wet season, and rest during the 
dry—when there is one, for a number of species grow where the seasons 
are fairly equable, and these can scarcely be said to have a distinct season 
of rest. Such Orchids probably suffer most during our long dull winters, 
and this is probably the cause of a number of desirable Orchids being 
considered intractable subjects. True epiphytes are easily recognised by 
their fleshy, aérial roots, covered with a white outer layer, from which 
protrudes a green point when the roots are growing actively. In such 
cases the provision of a suitable atmosphere is especially ops ates because 
so many of sexs roots are outside the compost. 
