Part II: THE WORLD OF
PLANTS
By now you have examined the simpleststructuralunits of living things,
cells; you know somethingaboutthe mysterious life-giving substance called
protoplasm;you have seenchloroplasts containing chlorophyll, the equally
mysterious substance in the leaves of green plants on which all life is
dependentfor food. You are well under way in your studyofbiology.
Now you will venture into the vast and varied world of plants. Ofcourse,
some plants are well known toyou-theapples or oranges you eat, the seaweed
washed up on the beach, the sweet peas which may grow in your mother's
gardenor those energeticdandelionsthatmake a nuisance ofthemselves by
poppingup all over the lawn in spring and summer.
But there arehundredsand hundredsofother plants, less well known
thanthese. Some grow low on the floorofwoods and forests, or on the sides
ofrocks and trees. Amongthese are the ferns, mosses andmushroomswhich
you will study soon. Some plants (elodea, for example) grow only inwater;
others, like the familiar oak, elm and maple trees, grow only on land. It
won'tsurprise you to hearthatplants vary in size, but do you knowhow much
theyvary? The giantredwoodtrees inCaliforniasometimes grow as high as
300 feet. On theotherhand,there are many plants so smallthatyoucannot
see them withouta microscope. Amongthese are various kinds ofbacteria
and plants called"algae"which live in ponds and streams.
Manydiscoveries await you in the following pages. You will learn how
greenplantsmanufacturetheir own food and how they manage to reproduce