The use of the _Waldfeldbau_ (combined farm and forest culture) was also inaugurated for the purpose of cheapening the cost of plantations (by v. Langen in 1744) when the great movement for reforesting wastes and openings began, the tree seed being sown with the grain either at once or after farm use for some years. Regular annual planting budgets (of $50--$100--$200) were inaugurated in Brunswick by v. Langen in 1745; and in 1781, the Prussian forest administration had attained to entirely modern planting plans and annual planting budgets. It was no wonder that the fear of a timber famine and the apparent hopelessness of bringing improvement into the existing forest conditions created anxiety and a desire to plant _rapid growers_, such as birch, willow, aspen, alder; the planting of the White Birch became so general in the beginning of the 18th century that a regular betulomania is recorded corresponding to the incipient catalpomania in the United States. At that time, to be sure, firewood was still the main concern, and the use of these rapid growing species had some justification. But where birch was mixed in spruce plantations its baneful effects consisting in whipping off the spruce tips and injuring its neighbors were soon recognized, and much trouble was experienced in getting rid of the unwelcome addition. The _Robinia_, which had been brought from America in 1638, was also one of the trees recommended in the middle of the 18th century and was much planted until Hartig pointed out that the expectations from it were entirely misplaced. Of course no building material could be expected from these species, hence the larch, also a rapid grower, was transplanted from the Alps (1730 in Harz mountains), and its use was extended, as with us, to conditions for which it was not adapted. It was principally a desire for novelty and perhaps for better, especially foreign things, that led to the planting of North American species in parks during the first half of the 18th century. But, although F. A. J. von Wangenheim’s very competent writings on the American forest-flora and on the laws of naturalization (1787) stimulated interest in that direction, the use of American species for forest planting was not inaugurated till nearly 100 years later, with the single exception of the White Pine (_P. strobus_), of which large numbers were planted. 7. _Improvement of the Crop._ Thinning of stands had been practiced early in the 16th century, not for improvement of the remaining stand so much as to secure fence material, although in 1531 the observation was already recorded that thinning improved and stimulated the remaining growth.