Whenever plants begin to drop their leaves, it is certain that their health has been injured; this maybe due to over-potting, over-watering, over-heating, too much cold, or the application of such stimulants as guano, or to some other cause which has destroyed the fine rootlets by which the plant feeds, and induced disease that may lead to death. The case is not usually important enough to call in a "plant doctor," so the amateur begins to treat the patient, and the practice is in all probability not unlike that of many of our household physicians who apply a remedy that increases the disease. Having already destroyed the, so to speak, nutritive organs of the plant, the stomach is gorged with food by applying water, or with medicine, by applying guano or some patent "plant food." Now the remedy is nearly akin to what is a good one when the animal digestion is deranged - give it no more food until it re-acts. We must then, if the roots of the plant have been injured from any of the above named causes, let the soil in which it is potted become nearly dry; then remove the plant from the pot, take the ball of soil in which the roots have been enveloped, and crush it between the hands just enough to allow all the sour outer crust of the ball of earth to be shaken off; then re-pot in rather dry soil, (composed of any fresh soil mixed with equal bulk of leaf-mold or street sweepings), using a new flower-pot, or the old one, thoroughly washing it, so that the moisture can freely evaporate through the pores. Be careful not to over-feed the sick plant. Let the pot be only large enough to admit of not more than an inch of soil between the pot and ball of roots. After re-potting, give it water enough to settle the soil, and do not apply any more until the plant has begun to grow, unless indeed the atmosphere is so dry that the moisture has entirely evaporated from the soil, then of course water must be given, or the patient may die from the opposite cause - starvation. The danger to be avoided is in all probability that which brought on the sickness, namely: saturation of the soil by too much water. Other causes may induce sickness in plants, such as an escape of gas in the apartment, or smoke from a flue in the greenhouse, hut in all cases, when the leaves fall from a plant, withhold water, and if there is reason to believe that the soil has been poisoned by gas, or soddened with moisture, shake it from the roots as before advised, and re-pot in a fresh flowerpot. Many years ago, when I used smoke-flues in my greenhouses, some kindling wood, carelessly thrown on the top of one of them, ignited, and the smoke caused the leaves of every plant to drop. There were some 3,000 plants, mostly Tea-Roses, in the greenhouse; it would have been too much of a job to re-pot all, but by withholding water for some ten days, they started a new growth again, and very few plants were injured.