Botanical tracts, by Dr. Hill, viz. I. Usefulness of a knowledge of plants 2. Outlines of a system of vegetable generation. 3.The origin of double flowers. 4 The origin of proliferous flowers. 5. The sleep of plants. 6. The history and virtues of valerian 7. An account of the mushroom stone. To which are added 1. The method ... by Mr. T. Barnes, ... 2. The practice ... by Mr. T. Perfect. Publish'd at various times. Now first collected together.