Botany is study of plants, including algae, fungi, lichens, mosses, ferns, conifers and flowering plants. Collections at the Academy, which are housed in the Philadelphia Herbarium (PH), the oldest institutional herbarium in the New World, include some of the oldest and most important botanical collections in the Americas. Notable early collectors include Benjamin Smith Barton, Constatine Rafinesque, Thomas Meehan, Thomas Nuttall, and Fredrick Pursh. Today, the herbarium contains approximately 1.5 million specimens of vascular plants, fungi, lichens, algae, and fossil plants, 40,000 of which are types. It also contains some special collections, including the plants collected by Johann and Georg Forster during the voyages of Captain James Cook, and by Meriwether Lewis during the Lewis and Clark expedition (Corps of Discovery). The department's current focus is plant biodiversity and evolution focusing on Apocynaceae (milkweed or dogbane family) and Polygalaceae.