At all times be very careful of the temperature of this department, and more especially at this season of the year, as a few minutes' neglect might materially injure many of the delicate plants. The thermometer ought to range between 58° and 65°. In fine sunshine days, admit a little air by having some of the top sashes let down, one, two, or three inches, according to the weather, and let it always be done from eleven to one o'clock; but by no means in such a manner as to cause a draught in the interior of the house, which would be very prejudicial. Therefore be always cautious during cold weather, in administering that necessary element to vegetation, which is so conducive to health.

OF FIRING AND FUEL.

The Hot-house ought never to be left entirely to inexperienced persons, because they are not aware of what might be the result of inattention even for an hour. Attention to the following observations will obviate every difficulty. About this season of the year, frost generally sets in very severe in the middle states. Suppose the day may have all the clemency of spring, the night may be directly the reverse. Every precaution is necessary to guard against extremes. According to what was said last month, it is understood that the shutters are put on every night at sundown, and in severe weather, they must be put on as soon as the sun goes off the glass. If the shutters are omitted till late in severe frost, it will so reduce the heat of the house, that you cannot overcome it by fire until near midnight; and when done, the fire or fires have been made more powerful than they ought to be, proving uncongenial to the plants that are near the flues. The air, as above directed, having been taken off the house at one o'clock, as soon as the mercury begins to fall in the thermometer, kindle the fire, and supposing it is anthracite coal, in twenty minutes, with a good drawing furnace, the heat will operate in the house. If a coal fire, kindled about four o'clock, it will require an addition about six, and then may be made up again about nine or ten, which will suffice until morning. The quantity must be regulated by the weather. If the fuel is wood, it must be attended to three or four times during the evening; and when the mornings are intensely cold, one fire in the morning is requisite. When there are bad drawing furnaces the fires must be made much earlier, perhaps by two or three o'clock, which will be easily observed by the time the fire takes effect upon the air of the house. The temperature ought never to be under 55° of Fahrenheit.

OF WATERING THE PLANTS.

To do this judiciously, is so necessary to vegetation, and so requisite to understand, and yet the knowledge so difficult to convey to others (being entirely acquired by practice,) that if the power was in man to impart it to his fellow-men, he would possess the power of perfecting a gardener by diction. However, the hints on this important point of floraculture, will be as clear and expressive as can at present be elicited. All plants in this work that are aquatic, shall be specified as such; and those that are arid shall be duly mentioned. All others will come in the medium.

All the plants must be looked over every day, and those watered that appear to be getting dry on the top. It must be strictly observed not to give water to any but such as are becoming dry, and let it be given moderately at this season. Two or three days may perhaps elapse before it need be repeated. There is not so much liability to err at present in giving too little, as in administering too much. Vegetation amongst the stove or Hot-house plants will soon begin to show, and the soil will prove uncongenial if it is impregnated with stagnant moisture. Small plants should always be watered with a pot, having what is termed a rose upon it. The surface of the rose, that is, where it is perforated with small apertures, ought to be level, or a little concave, which would convey the water more to a centre, and make neater work, by preventing any water from being unnecessarily spilt in the house. The size of the pot will be regulated by the person to suit the conveniences of the place. Water, when applied either to the roots or foliage of the plants, should be about the medium temperature of the house. The cistern, built on the plan herein recommended, will always give this, and sometimes more, which can easily be reduced by adding cold water. Where there are no cisterns, a tank or barrel might be in the house, in which the water could stand for one night or more, as is most suitable. When water is given without being thus aired, it chills the roots, prevents a luxuriant growth, injures the fresh and healthful appearance of the foliage, and too frequently gives to all the plants a sickly hue.

OF INSECTS, THEIR DESTRUCTION, &c.

In this department, insects begin to increase by hundreds, and too frequently their ravages are very obvious before their progress is arrested. We will treat of those which are most common, under their respective heads, with their nature and cure, as far as has come under our observation.

Aphis rosÆ, of the natural order of Hemiptera, or what is commonly known by Green Fly, Green Lice, &c. infect plants in general, and are particularly destructive in the Hot-house to HibÍscus rÒsa-sinÉnsis, AsclÈpias, CrÁssula coccÍnea, AlstroemÈria, and many other plants of a free growing nature. They attack the young and tender shoots at the point, leaving a dark filthy appearance on the foliage. Many remedies for their destruction have been offered to the public by various writers, each equally secure in his own opinion. Extensive practice alone can show the most easy and effectual cure. Fumigating with tobacco is decidedly the most efficacious, and in the power of any to perform. Take a small circular furnace, made of sheet iron, diameter at top twelve inches, and at bottom eight; depth one foot, having a grating in it to reach within three inches of the bottom, which will leave space for the air to pass, and where the ashes will fall and be kept in safety, having a handle like a pail to carry it with. This, or any thing similar, being ready, put in it a few embers of ignited charcoal; take it into the centre of the house, and put on the coals a quantity of moist tobacco stems. If they attempt to blaze or flame, sprinkle a little water over them; and as they consume, continue to add tobacco until the house is entirely full of smoke, observing always to do it in still, cloudy weather, or in the evening. If it is windy, the smoke is carried off without having half the effect, and requires more tobacco. The house must be closely shut up. There are several plants whose foliage is of a soft downy nature, such as HelitrÒpiums, CallacÁrpas, SÁlvias, and many of the LantÀnas, VÍncas, with several others, that cannot stand, without danger, strong fumigation. These should be put low down in the house, or under the stage. These fumigations will have to be repeated frequently, the time for which will easily be perceived; and, when required, ought not to be delayed. Several species and varieties of the same genus, Aphis, can be destroyed in the like manner.

Acaris tellurius, or red spider, is caused by a dry atmosphere, and its havoc generally is obvious before it is arrested. With its proboscis, it wounds the fine capillary vessels; and if the leaves are fine, they will appear as if probed with a needle, and yellowish around the wound. If they have farther progressed in their destructive work, the leaves will prematurely decay. On this appearance, turn up the leaf, and you will see them running about with incredible swiftness. Their body is of a blood colour, and their feet, eight in number, light red. When very numerous, they work thick webs on the under side of the leaf, and frequently all over it, forming a mass of half dead plants, decayed leaves, and thousands of spiders. The most effectual remedy is a thorough syringing with water, and profusely under the foliage. This being done every evening, will subdue and eventually banish them. Had the house been syringed two or three times per week, these intruders would not have appeared. It is said by some writers, that watering only reduces them to a temporary state of inaction, and will not destroy them. Laying aside the many prescribed nostrums, we assert that the pure element is the most effectual cure, as well as the most easy to be obtained.

Thrips, order Hemiptera, are insects so minute as scarcely to be perceptible to the naked eye. They generally lurk close to the veins of the leaves of plants, and frequently attack esculents. When viewed through a glass, they are seen, when touched, to skip with great agility. The larva is of a high brown, or reddish colour. The thrip has four wings, and walks with its body turned upwards. It frequently attacks the extremities of tender shoots, or young leaves, which become shrivelled, brown, and will rub to dust easily between the thumb and finger. When any leaves or shoots are perceived to be so, if you do not observe the green fly, expect the thrips. They may be destroyed by a fumigation of tobacco, in the same manner as the green fly. By the simple and expeditious method of fumigation, these insects and several others may be destroyed effectually at any time they appear.

Cocus hesperidus, or mealy bug, has appeared in the Hot-houses about Philadelphia within these few years, and, if not instantly destroyed, increases rapidly. It is of a white dusty colour, when broken, of a brownish red, generally covered with down, under which it deposits its eggs; and they, in a few months, come forth in great numbers. The cocus generally is of a dormant nature, but, in warm weather, they may be seen moving rapidly up the stems of the plants. Fumigating has no observable effect on these insects; therefore, as soon as they appear, recourse must be had to other means. The liquid made from the following receipt, is death to any of the Cocus tribe: Take two pounds of strong soap, one pound flour of sulphur, one pound of leaf tobacco, one and a half ounce of nux vomica, with a table spoonful of turpentine, which boil in four gallons of river water to three; then set aside to cool. When boiling, stir it well with a stick, continuing to do so until it is reduced as above. In this liquor immerse the whole plant, drawing it to and fro gently, that the liquor may penetrate every where.

This done, lay the plant on its side, until it begin to dry, then syringe well with clean water, and put it in its respective station. Where a collection of plants is free from any insects of the kind, every plant that is introduced, ought to be minutely scrutinized, that the unclean may be kept from the clean: the above insect will feed almost on any plant, but indulges on CrÁssulas, any of the bristly CÁctus, GardÈnias, and in fact whatever is in the way.

Cocus————, or brown scaly insect, is frequently found on many plants, but we never could perceive that it does any other material injury, than dirtying them. We have always observed, that it is found in winter to abound most in those situations which are most excluded from air; therefore is of less importance than the other species, which eat and corrode the leaves of tender plants. A washing with strong soap suds will destroy them, or the above liquid will do it more effectually. Tie a piece of sponge on the end of a small stick, and scrub every leaf, stem, and crevice. Fumigating destroys the larvÆ of this species.

Cocus————, or small white scaly insect, which generally infests Cycas revolÙta and circinÀlis, the varieties of NÈrium oleÁnder, Oleas, and several species of Acacias, may be destroyed by washing as above with a sponge, and a strong decoction of tobacco, using the liquid about the warmth of 100°. Being thus heated, it irritates the insect, when, by easing itself from its bed, the fluid passes under it, and causes immediate death. If it is not thus irritated, it adheres so closely to the foliage, that it will keep you at defiance. The under, or dark side of the leaves is its residence; and we have observed a plant in a house where there was only light on one side, with the dark side literally covered, while the light side was clean. So much for having houses with plenty of light. The effects of this insect are of a corroding nature, extracting all the juices from the leaf under it, even straining to the other side; and where they have got to the extremity, the foliage is completely yellow, and of a decayed appearance.

Cocus————, or turtle insect. We have never observed this insect arrive to any extent, but think that the Datura arborea is most infested with it. It is the largest of any genus known amongst us, and very like a turtle in miniature. On lifting it from the wood, to which it generally adheres, there appear to be hundreds of eggs under it, but fumigating completely destroys the larvÆ. In our opinion this turtle insect is no other than the old female of the brown scaly insect, which swells to a large size before depositing its eggs. We have frequently observed the insect dead in this enlarged state, and question if this is the last stage of its transmigration. The male insect is winged, and very active in its movements.

OF SHIFTING PLANTS.

At this period of the season very little is required to grow CalceolÀrias to perfection. They require a few months of the Hot-house, and if the directions given last month were followed up, some of these will have advanced a little in growth. The herbaceous kinds, when grown about one inch high, ought to be divided, and put into four inch pots, sprinkled gently, and kept in the shade until they begin to grow; after which, keep them near the glass, to prevent them from becoming spindly and drawn. Their farther treatment will be observed as they require. This is a beautiful genus of plants, flowering very profusely all summer, and some of them early in spring.

AlstroemÈrias, about the beginning or middle of the month, will have made their appearance above ground. When shot about one inch, turn them out, and carefully shake them clear of earth; and if required, divide the crowns, and put them in as small pots as possible, taking care not to break any of the strong fleshy roots. (For Soil, see Table.) To flower these plants well, they require to be frequently shifted, during their active stage of growth, which must be duly observed. The most of the species of this genus will more than repay the attention, by their abundantly and beautifully spotted flowers. A. flÓsmartÌna, A. PelegrÌna, A. pulchÉlla, and A. atrÓpurpurea, are the most splendid. The former flowers very freely. All natives of South America.

Where bulbous roots, such as Hyacinths, Jonquils, Narcissus, Ixias, LachenÀllas, &c. are required to be early in flower, they may, about the beginning or end of the month, be put in the front of the Hot-house, giving very little water until they begin to grow; then water freely, and tie up the flower stems as they advance.

OF CLEANSING PLANTS, HOUSE, &c.

This subject ought to be kept constantly in view. However correct every thing may be executed, without that adorning beauty, cleanliness, all will appear only half done. Therefore let all the dead leaves be picked off every day, and with dust and other litter swept out of the house, and when necessary, the house washed, which will be at least once a week. That the foliage of the plants may always appear fresh, syringe them in the evening, twice or three times per week; (when the weather is very cold, do it in the morning.) At present this will in a great measure keep down the insects, and will prove a bane to the red spider.

A hand engine is certainly the best. Milne's patent hand engine surpasses any that we have used. Nevertheless a hand syringe is very effectual. Some of these engines are powerful, throwing the water above forty feet. Read's patent of London is excellent. At the store of D. & C. Landreth, Phila., there is a very good kind, which answers admirably in small houses. Tie up neatly with stakes, and threads of Russia mat, all the straggling growing plants; let the stakes be proportionate to the plants, and never longer, except they are climbing sorts. Do not tie the branches in bundles, but singly and neatly, imitating nature as much as possible. If any of the plants are affected with the Cocus insect, let them be cleaned according to the plan already mentioned, taking particular care also in washing the stakes to which they had been previously tied, and burning all the old tyings, which contain the larvÆ of the insect in many instances, especially of Cocus hesperidus. It is premised, when any of these things are done, that they will be well done, and not half doing, and always doing. Cleanliness, in every respect, promotes a pure air, which is congenial to vegetation, and will, with other attention, always ensure a healthful and vigorous appearance in the house.