INTRODUCTORY 5 



we have not seen, to see things as they are, to properly inter- 

 pret what we see and to make accurate records of our observa- 

 tions and interpretations. A knowledge of chemistry, physics 

 and geology is necessary for a thorough understanding of botany 

 and a knowledge of botany is necessary for the highest develop- 

 ment of agriculture, agronomy, horticulture, floriculture, for- 

 estry, plant pathology and other applied branches of the subject. 



Plants are more or less generally distributed over the greater 

 part of the earth's surface, and in many cases are the most pre- 

 dominant features in the landscape. Some live in very dry 

 regions, while others are found in the swamps, and still others 

 are attached, or floating in both fresh and salt waters. In fact, 

 the animal life of the waters is dependent on the aquatic plants 

 in the same manner that land animals 1 are dependent on land 

 plants. Some plants live in the very cold parts of the earth, 

 while others live in the extremely warm regions; in fact, some 

 of the low forms of plants live in hot springs at a temperature 

 approaching the boiling point, Some plants live on other plants 

 and some live on animals. A very few parts of the earth, such 

 as the extremely cold regions, volcanic areas, desert regions and 

 certain salt deposits are without plant life. A knowledge of the 

 features of the earth's surface combined with a knowledge of the 

 conditions necessary for the growth of different species of valu- 

 able, economic plants, has enabled man to introduce plants from 

 one part of the world to other parts with great profit to the 

 human race. Some of the arid and semi-arid regions have been 

 irrigated and the conditions so changed as to make high plant 

 production possible. 



Plants vary greatly in form and general appearance. Some 

 of them are so extremely small that they cannot be seen without 



