4 SCIENCE PRIMERS. [i. 



powdery crusts they cling to the hardest rocks and 

 stoniest soils of mountains and moorlands ; as moulds 

 they spoil articles of food, books, leather-work, woollen 

 and other fabrics ; as dry-rot, and under many other 

 forms, they utterly destroy trees, wooden houses and 

 ships ; as smut, rust, bunt, potato- and vine-blight, 

 they prey upon the living tubers, stems, leaves, and 

 fruits of the most valuable crops, and some even 

 invade the organs of living animals. 



Things Necessary to the Life of Plants are 

 air, heat above the freezing point, light, water, and 

 earthy (inorganic) matter in some shape. The ex- 

 ceptions to this are few ; amongst them are the Red- 

 snow plant, a most minute vegetable, which 'tinges the 

 surface of melting snow with a rosy hue ; and fungi, 

 of which some grow or are cultivated in total dark- 

 ness. No plants, except these, continue to live in 

 health in the absence of light, as a few blind animals 

 can do (fishes and insects) which inhabit caves, as 

 well as many deep-sea animals, and those that live in 

 the interior of others. 



The Division of Labour in Plants. During 

 their life-time plants perform various kinds of work 

 which are essential, some to sustain them in life and 

 health, others to reproduce their kind. These kinds 

 of work being very different from one another are not 

 accomplished by any portion of the plant indiscrimi- 

 nately but are carried on by particular parts specially 

 fitted for the purpose (called organs). 



In the case of flowering plants, for example, the 

 principal Organs are, i. The Root, by which the 

 plant is fixed to the ground, and absorbs /nourishment 

 from it; 2. The Stem, which supports the buds, 



