72 
OPERATIONS FOR APRIL. 
in the day-time, ought now to be carefully sustained. We have recently seen it 
stated, by a respectable authority, that Orchidace^ never thrive in those countries 
where extremes of heat and cold are not experienced between the day and night, 
which may serve as a useful hint respecting the inutility of evening fires for the 
Orchidaceous house. 
As far as relates to increased humidity or heat, the principles above propounded 
should regulate the management of the Stove. Tropical plants grow solely at 
those times when the temperature of the air is excessive, and fluids float most 
abundantly therein ; — a fact which at once decides the accuracy of the preceding 
direction. 
"With reference to greenhouse species, these rules, though appropriate, must be 
largely modified. It will not do to keep a greenhouse too confined, in order to 
raise the temperature, since this would at once convert it into a stove. Any course 
of that kind is, in fact, rendered needless by a remembrance of the simple truth, 
that in a glass structure, how^ever much air may be admitted, the heat will still 
remain far above that of the external air. Free ventilation is therefore greatly to 
be desired, inasmuch as it tends to produce a healthy growth, to moderate the 
otherwise superfluous heat and evaporation, and render the house more comfortable 
to the visitor. In providing it, however, it must be seen that hurtful winds are 
excluded. 
To preserve a continuous moistness in the air of the greenhouse will be next to 
impossible. The best substitute for this is liberal waterings at the root, which will 
cause constant evaporation, and occasional springings in the evening of fine days, 
by which the double purpose of supplying moisture and purifying the leaves of 
plants is answered. 
All the plants in pits or frames whose transference to the flower-borders is 
contemplated next month, may be now gradually acquiring hardihood by being left 
uncovered with the lights in the day, and also throughout the night, when the 
weather permits. Some of them will show an early disposition to develop flowers; 
but the buds are to be timely extracted. In proportion to the extent to which this 
removal of flower-buds is carried, the summer's display will be either scanty or 
brilliant. 
Annuals may be sown for succession ; Chrysanthemums, Rockets, and all kinds 
of plants may be propagated from cuttings ; climbers must be trained as they grow ; 
tender annuals should, if worth it, be potted into small pots, that they may 
be transplanted with greater facility ; Dahlias and the sorts allied to them in habit 
are to be hardened ready for planting ; but we would not have the summer orna- 
ments of the flower-beds placed in their final position till the beginning of the 
succeeding month. 
