Growing vegetables under glass gives smaller returns than flowers; as, for instance, a head of lettuce brings much less than a plant of carnations, and suffers more from the competition of southern crops. Nevertheless, the greenhouse-grown vegetables have come into prominence lately because they can be raised in houses that are not good enough for flowers. Lettuce and tomatoes are the principal crops; some growers raise thousands of dollars' worth each year. The greenhouse is also used for forcing plants which are afterwards transplanted to the open air. This develops them at a time when they could not grow outdoors and gives them such a start that they are very early on the market, thereby realizing the highest prices. "Nearness to market is the most important feature in a greenhouse. In large cities, manure, which is the chief fertilizer, can be had in most cases for the hauling. The short haul is an important item, and, most important of all, the gardener who is near the market can take advantage of high prices, if the grower is near enough to the city to make two or three trips; in such a fluctuating market as New York, it is to his advantage." Some kind of a greenhouse is necessary, but one large enough to produce a living would cost a very large sum. Vegetable raising under glass has been made profitable in special localities where nearly the whole community gives its time to building up the industry, but complete success can be attained only by having absolute control of all the conditions entering into production, and giving assiduous and undivided attention to detail. Leonard Barron, in the _Garden Magazine,_ says: "The best type of greenhouse for all-round purposes is unquestionably what is known as the even span--that is, a house in which the roof is in the form of an inverted V, so as to be exposed as much as possible to sunlight, and having the ridge-pole in the center. All other types of houses are modifications from the simplest form, and are designed in some way or other to fit some special requirements. These requirements may be: the cultural necessities for some particular crop; a desire to have the atmospheric conditions inside more or less abnormal at given seasons (as in a forcing house); or an adaptation to some peculiarity of the situation, as when a greenhouse is built as an adjunct to other buildings."