No operation in the greenhouse requires more care and good judgment than watering, especially where there is a general collection of plants, some of which require an abundance of moisture at all times, while alongside there is a plant probably requiring to be kept on the dry side. A single thermometer can govern a house full of plants as to temperature, but, it requires with watering individual attention. The soil may be suitable, the light, heat and ventilation all that is necessary; if the treatment with regard to water has not been properly and timely attended to disappointment shall be the result.

We are apt to look upon the soil or the temperature as being the essentials to the successful culture of plants; often questions are asked relative to these two requirements, but how seldom do we hear the watering inquired about; everybody appears to think they can supply water according to the plant's requirements, but this is a mistake. The most successful gardeners and florists in the country to-day, are those who give the closest attention to watering, and while they cannot describe orally or in writing the exact conditions for successful watering, they look upon it as the base of their success.

The geographical distribution of plants should be one of the main studies of the successful gardener, so that the natural conditions in their native habitats be known. We also want to know the conditions of moisture, atmospheric and otherwise, the daily and nightly temperatures, their seasons, and how long the plants rest. It is not enough to know that a plant comes from a certain country, as altitude makes a wonderful difference as regards atmospheric conditions. Take some of our cool growing orchids, from the high altitudes of Central America, and try to grow them in the same conditions as regards temperature and humidity that are found on the sea-level in that country, and failure would be the result.

Although in a good many cases we can improve the conditions of plants by departing from their natural state as regards soil and temperature, still the same degree of humidity should be closely adhered to.

A general knowledge of vegetable physiology to the gardener is the light which successfully pilots him through the dark avenues of difficulties, which are continually being met while endeavoring to cultivate plants collected from almost every point of the universe. How is this knowledge to be acquired but by studying the works of men who have given it their special study.

The Gardeners' Monthly is the only periodical in the country from which any light on vegetable physiology can be obtained; if there is another please give me the name of it.

I do not mean to say but that there have been, and are still, men who are very successful gardeners and florists who could not tell you anything scientifically about plants, but these same men are practicing and demonstrating by their practice the true requirements of plant life, which have been acquired by years of close study and observation. Youngstown, Ohio, September 12, 1887.