2 INTRODUCTORY 



such as carbon dioxide, water, and various minerals. Although 

 these points of difference between plants and animals are 

 suificient to separate the two classes from each other, so far as 

 the purposes of everyday life are concerned, it must be mentioned 

 that a further examination of living things shows that there are 

 some which in structure and power of utilising inorganic sub- 

 stances as food-materials resemble plants, but which are never- 

 theless able to move about as freely as animals, and that other 

 structures usually considered as animals move very little. Then, 

 again, there are living things always classed as plants, which pro- 

 duce flowers and seeds, although they cannot live when supplied 

 with carbon dioxide, water and minerals, but must be fed upon 

 the same or similar substances to those needed by animals. 

 Indeed, all attempts to draw a hard line of separation between 

 plants and animals are found to end in failure. The living sub- 

 stance within them appears to be the same, and between the so- 

 called animal and vegetable kingdoms there is no distinct point 

 of difference. The living world is essentially one, and not two, 

 and it is very necessary to constantly bear in mind that plants 

 are just as much living structures as animals are, since by far the 

 larger number of mistakes in the management and cultivation of 

 plants are due to want of proper appreciation of this fact. 



2. For the present our attention will be confined to the common 

 plants of the farm and garden. In form and structure these 

 are altogether different from animals, and as the difficulty of 

 defining the two classes of living things is only met with in 

 studying minute and practically unseen organisms it may be 

 dismissed for the present. 



It will be readily understood that plants may be studied from 

 a great many different points of view, and consequently special 

 branches or divisions of the science arise. Attention may be 

 confined to an investigation of the uses of the various parts of a 

 plant's body— to the work which the leaves, roots, and flowers 

 perform in the life of the plant ; this part of the subject is known 



