6 SCIENCE PRIMERS. [i. 



substances, such as resin, sugar, oil, wax, and colouring 

 matters, 



The Reproduction of Plants takes place in 

 two ways. First, and principally, by seeds ; secondly 

 by buds that separate and grow into independent 

 plants. Seeds are produced by the interaction of 

 special organs of two kinds, and are inclosed in a 

 covering called the fruit. Buds that separate them- 

 selves and become new plants are formed on various 

 parts of plants, as where the leaf is attached to the 

 stem in the tiger-lily and the tubers or underground 

 branches in the potato plant. 



Many plants may be artificially increased by divi- 

 sion ; that is, by cutting off a twig with a bud on it, 

 and sticking it into damp ground, when the twig will 

 send forth roots. Or the twig may be inserted into a 

 slit in the branch of a similar tree, with which it will 

 unite, and the bud thus nourished will grow, and pro- 

 duce leaves, flowers, and fruits. 



The Tissues of Plants. The substance of 

 plants is not, like a piece of stone, made up of 

 particles in which no definite form or structure is 

 visible, but is built up of minute bags called cells, and 

 of tubes called vessels (which also consist at first of 

 rows of cells), packed more or less closely together. 



The Chemical Constituents of Plants. 

 Plants, like animals, contain a far greater weight of 

 water than of anything else. Besides the elements 

 of water (oxygen and hydrogen), the tissues contain 

 carbon (which is the charcoal left after burning), and 

 some also contain nitrogen. Plants obtain the water 

 principally by their roots; the carbon by their leaves 

 .rom the carbonic acid gas absorbed from the air, and 



