Bark (botany) rope, used for example in the rigging of Viking age longships. Among the commercial products made from bark are cork, cinnamon, quinine (from the bark of Cinchona) and aspirin (from the bark of willow trees). The bark of some trees notably oak ("Quercus robur") is a source of tannic acid, which is used in tanning. Bark chips generated as a by-product of lumber production are often used in bark mulch in western North America. Bark is important to the horticultural industry since in shredded form it is used for plants that do not thrive in ordinary soil, such as epiphytes.
Asa Gray Gray had to borrow money from his father. Soon he was able to repay his father and help his family by supplementing his income giving lectures outside of Harvard, including at the Lowell Institute. Gray was considered a weak lecturer, but because of his expert knowledge, he was highly regarded by his peers. His skills were better suited to teaching advanced rather than introductory classes. He also gained renown for his textbooks and high quality illustrations. Gray moved into what became known as the Asa Gray House in the Botanic Garden in the summer of 1844. It had been built