The credit of having radically changed these practices belongs to Pfeil, who, entirely reversing his position, advocated for pine forest a system of clearing followed by sowing, or by planting of wildlings with a ball of earth. Then, suggesting that possibly planting without this precaution could be attempted, and pointing out the necessity of securing a satisfactory root system, he recommended, about 1830, the use of one-year-old seedlings grown in carefully prepared seed beds. While for securing these, he relied upon the simple preparation of the soil by spading, _Biermans_ added the use of a fertilizer in the shape of the ashes of burned sod. The method of growing pine seedlings and planting them when one to three years old was further developed by _Butlar_ (1845), who introduced the practice of dense sowing in the seed beds. He also invented an ingenious planting iron or dibble, a half cone of iron, which was thrown by the planter with great precision, first to make a hole and then to close it. This was improved by the addition of a long handle into the superior, well-known and much used _Wartenberg_ planting dibble. At the same time (1840), _Manteuffel_ devised the method known by his name of planting in mounds, which is especially applicable on wet soils. It was not until 1840 that transplanting of yearling pines with naked roots became general. The widespread application of this latter system resulted in abandoning to a large extent mixed growth, and led to the establishment of pure pine forests, introducing thereby most intensively all the dangers incident to a clearing system and pure forest which are avoided by the mixed forest, namely, insects, frost and drought. A practice of planting spruce in bunches, originally twelve to twenty plants in a bunch, had been in existence since 1780. This practice increased until 1850, and is still in use in the Harz mountains and in eastern Prussia, although the bunches have been reduced so as to contain only from three to five plants, the object of the bunching being to make sure that one or the other of the plants should live. Much discussion as to the merits of this method took place between the old masters, Cotta favoring the small bunches upon the basis of a successful plantation of his own, Hartig and Pfeil opposing it, but finally weakening. Since 1850, however, the practice of setting out single plants has become more general.