The green plants live an Independent life. With the sunlight for a motive force, they combine the carbon dioxide of the air with water to form much of their tissues. With a few more elements taken from the soil, they are self sufficient.

   Other great groups of plants have been "on relief" so long as to lose their chance of independence. Now with their chlorophyll gone, they must live as parasites or saprophytes and like all the animals are directly or indirectly dependent upon the green plants for food. The green plants then become king of all living things.

   Plants on the whole display a wide range of sizes. Some bac­teria are so small that more than six thousand billion would be required to fill a cubic inch of space. At the other extreme, vines occasionally exceed a length of one thousand feet. Now and then a tree may be over 300 feet high with a trunk more than 30 feet in diameter.

   One tiny bacterium would have about the same size ratio to the big tree as a well fed house-mouse would have to the entire earth and all that is in it.

   The best way to know and understand plants is to live with them. For the student, some collecting or research project if thoughtfully pursued is sure to pay well in pleasure and knowl­edge. "How to Know the Trees" suggests 25 tree study projects (p. 13) while In "Living Things-How to Know Them" a chapter Is entitled "More than 100 Suggestions for Nature Study Projects" . These offer many good suggestions to which the ingenious teacher or student can readily add other good ones.

   Plants that have common everyday uses or relationships are known by "common names". In fact, many of them have several com­mon names and that is how the trouble begins. For instance, Abutlion theophrasti, a widely distributed and all too abundant Asiatic weed, Is referred to by the following, Velvet leaf, Indian Mallow, Butter-print, Button-weed, Ple-print, Mormon-weed, Cotton-weed, Indian Hemp, Sheep-weed, American jute, Pie marker, etc. If a plant is cosmopolitan each language may also have one or more names for it.

   To make the confusion still worse the same name is frequently applied to several different plants, leaving the hearer in doubt as to which one is meant.

   To ease this difficulty, Linnaeus, a Swedish naturalist around 1760, devised a system of scientific names which would be world wide in their application. He did such a good job that his scheme is still in use, and while it is not perfect the plan of having one universal scientific name for each plant has many advantages over common names.