6 A GENERAL VIEW OF PLANTS 
small that they can be seen on y with a microscope. Ranging 
from these very small plants to the largest trees, plants of all 
sizes and complexity occur about us. The different plant forms 
differ very much in structure, methods of getting food, and 
methods of reproduction. The plants which concern us most 
are those which have flowers. They are known as the Flowering 
Plants. Most of the cultivated plants and nearly all weeds 
belong to this group. They are the plants which furnish nearly 
all of our food and fibers and much of our lumber. Part I of 
this book is devoted to the study of the Flowering Plants. 
Although the Flowering Plants concern us most, it must not be 
concluded that the simpler plants are of no importance. The 
simpler plants, even the microscopic forms, not only help and 
hinder in the cultivation of the Flowering Plants, but affect us in 
other ways and must receive consideration. Much of Part II 
is devoted to the study of them. 
Parts of a Plant. — In plants, as in animals, there is a living 
body consisting of parts each of which has a special work to 
perform. The various parts of a plant having their own special 
work are called organs, and the special work of an organ is its 
function. Plants, like animals, being composed of organs, are 
called organisms. In the Flowering Plants, the plant body con- 
sists of roots, stem, leaves, buds, flowers, seeds, and fruit. All of 
these structures are not present at all times, but unless a Flowering 
Plant develops all of these organs during its life, its development 
is considered incomplete. Through the special functions of its 
organs, the plant is able to exist and reproduce itself. The roots 
hold the plant to the soil and furnish water and salts; the stem 
supports the leaves, flowers, and fruit in the air and sunlight; 
the leaves make food; the buds produce new leaves and flowers; 
and the flowers, seed, and fruit have to do with the production 
of new plants. But each organ is also composed of parts and to 
understand an organ one must understand its special groups of 
cells, known as tissues, of which the organ is composed. 
Life Cycle of Flowering Plants. — A characteristic of living 
organisms is their ability to use substances as food, grow, and 
develop. Living organisms are also much influenced by their 
surroundings. Plants are much influenced by the nature of the 
soil, air, sunlight, and plants which grow about them. 
To understand a plant one needs to study it in its various 
