SUBJECTS FOR HYBRIDISING 79 
on the seedling house, in addition to the lath roller blind, 
running on supports carrying it well above the glass of the 
roof, either a second lath roller blind running an inch or 
so above the glass and beneath the upper one, or a per- 
manent thin cotton shading, which may be tacked on in 
spring and left until autumn ; or, preferably, so fitted that 
it can be rolled up when it is not required, 
SELECTION OF SUBJECTS FOR HYBRIDISING 
The best varieties procurable should always be selected 
for hybridising, it having been proved that crosses originally 
made with indifferent varieties are much finer when raised 
again from more carefully selected varieties. 
There seems to be no certain limit to the possibility of 
crossing ; even the most dissimilar genera may be crossed 
with some probability of getting a successful result. 
POTTING MATERIAL FOR HYBRID ORCHIDS 
From the time the little plants are well established in 
single pots, the same potting material used for all of their 
kind may be employed, the plants in the earlier stage having 
the potting material in a finer condition than that provided 
for the larger plants as they approach the flowering stage. 
As with other important operations, in Orchid potting 
and in the material used the practice varies considerably, 
even in the best collections, and this points to the fact that 
if the accommodation is good, the houses properly heated, 
and other details of culture carefully carried out, the exact 
