ABSTRACT
Contemporary botanists distinguish between vascular and non-vascular plants. Vascular plants have xylem, tissue dedicated to transporting water within the plant. Non-vascular plants don't have xylem. Non-vascular plants, such as mosses and liverworts, evolved first, before vascular plants, such as sequoias and daffodils. In Carolus Linnaeus' Systema Naturae of 1735, he classified organisms simply into animals and plants, but biologists have learned a lot since then. Although they continue to debate how properly to classify organisms, many biologists now recognize two domains, Prokaryota and Eukaryota, which are divided further into six kingdoms: Bacteria, Archaea, Protista, Plantae, Fungi, and Animalia. Phototropism and gravitropism suggest that plants might perceive their environment. The currently dominant way of thinking about perception requires representation.
