_Two-storied Seed Forest._ A modification of the system of Regular Seed Forest is the planting of another and a tolerant species of tree under older intolerant trees to make a cover for the soil, to prevent the growth of grass and weeds, and to improve the quality of the upper growth.[2] An illustration of a natural two-storied seed forest is shown in Fig. 126. [Illustration: No. 126. Two-storied Seed Forest. Fir under Beech, Germany. _U. S. Forest Service._] _Planting._ The planting of forest trees is a comparatively unimportant part of modern forestry. It is a mistaken idea, not uncommon, that the usual way of reproducing forests is to plant trees. It is true that in the pineries of North Germany and in the spruce forests of Saxony, it is common to cut clean and then replant, but it is absurd to conclude, as some have done, that forestry consists of planting a tree every time one is cut. Even if planting were the best method, many more than one tree would have to be planted for each one cut, in order to maintain the forest. So far as America is concerned, not for a long time will planting be much used for reproduction. The greater portion of American woodlands is in the condition of culled forests, that is, forests from which the merchantable trees have been cut, leaving the younger individuals, as well as all trees belonging to unmarketable species. Even on the areas where the lumbermen have made a clean cut of the original timber, new trees will come up of themselves from seeds blown from the surrounding forests or falling from occasional individuals left standing. (Bruncken, p. 133.) The usefulness of planting in America is mainly for reclaiming treeless regions, as in the west, and where timber is high priced. The area of planted timber in the Middle West aggregates many hundred thousand acres, once waste land, now converted into useful woods.[3] Planting has been made possible in the far west by extensive irrigation systems, and farther east by the lessening of prairie fires, which once set the limit to tree growth in the prairie states. In many parts of Illinois, southern Wisconsin and other prairie States, there is much more forest land than there was twenty-five years ago. What planting can do, may be seen on some worn out pastures in New England, Fig. 127. With the western movement of agriculture, the abandoned farms of New England are to some extent becoming re-forested, both naturally and by planting, as with white pine, which grows even on sandy soil. Between 1820 and 1880, there was a period of enthusiastic white-pine planting in New England, and tho the interest died on account of the cheap transportation of western lumber, those early plantations prove that white pine can be planted at a profit even on sand barrens. Once worn out and useless pastures are now worth $150 an acre and produce yearly a net income of $3 or more an acre.