In the 1640s, the flemish chemist jan baptista van helmont performed the classic experiment paraphrased below: i filled a pot with 200 pounds of dirt that had been dried in an oven. then i planted the stem of a willow tree and watered it with rainwater. at the beginning, the willow stem weighed 5 pounds. for 5 years, i watered the tree with either rainwater or distilled water whenever it was needed. the pot was large, and planted in the ground. i covered the pot with an iron plate. this had many holes, which allowed water through but not dust. in this way, i could be assured that possible dust accumulation over these 5 years did not significantly add to the weight of the dirt. after 5 years, the tree weighed 169 pounds, and about 3 ounces. i did not take into account the weight of the leaves that fell each autumn. at length, i again dried the dirt, which weighed only 2 ounces less than the initial 200 pounds. i concluded that the 164 pounds of wood, bark, and roots, arose out of water only. in what way was van helmont's conclusion incorrect?