| The age-old experience of farmers is that fruits | | | | been put to other uses. In these glass-covered |
| grown on the protected, sunny side of a slope, | | | | gardens summer conditions may be maintained at any |
| mature earliest. This led the way to the development | | | | season of the year. Careful artificial heating is used in |
| of the modern greenhouse. Some of the early stages | | | | addition to the natural warmth of the sun. Smaller |
| of this development may be traced back to England, | | | | greenhouses may be heated more uniformly with hot |
| where it was the general practice to train grapevines | | | | water. For the larger ones, steam has proven to be |
| upon well-sunned garden walls. Some conceived the | | | | more economical and practical. In a greenhouse, |
| idea of inclining these walls so that the rays of the | | | | ventilation is Just as important as heating. The |
| sun might fall more directly upon the vines. Then, in | | | | regulation of the air supply is essential in controlling |
| an effort to protect the budding leaves from chilly | | | | temperature and humidity. It is vital to avoid sudden |
| breezes and sudden frost, glass coverings were built | | | | changes in either. |
| around them. When the warmth from the sun was | | | | The commercial advantages of greenhouses |
| considered insufficient, flues were placed in back of | | | | gardening can readily be seen. If a gardener can |
| the wall to furnish additional heat. The resulting | | | | force the growth of his vegetables several months in |
| lean-to form of greenhouse soon became an | | | | advance of the regular season, he can compete with |
| independent structure of glass supported by beams | | | | the produce shipped from southern climates. He can |
| of wood and of metal. | | | | also send some of his crops to market before those |
| Greenhouses were originally used for growing flowers | | | | in his locality have matured. |
| out of season. More recently, greenhouses have | | | | |