CHAPTEK XIX. 

 THE PLANT IN ACTION. 



EXERCISE LXXV. 

 Absorption of Food by Plants. 



As long as a seed is kept dry, the embryo remains 

 unchanged ; but, planted in the soil, under the influ- 

 ence of moisture and warmth, it begins to grow to 

 increase in size and weight, and to develop new or- 

 gans. At the same time, the rest of the seed withers 

 and disappears. It has been used up by the growing 

 embryo, while rooting itself, and opening its leaves 

 to the light and air. The plant now goes on inde- 

 pendently, adding new material to its substance, in- 

 creasing its size and multiplying its organs. 



Now, how do growing plants get the materials for 

 this increase of substance ? 



This is done in three ways. The first is known 

 as the principle of capillarity. This is the attraction 

 of surfaces for liquids, which causes the flow of 

 water upward into sponges and porous bodies gener- 

 ally ; and its rise in glass-tubes, with small openings 

 like hairs, and hence called capillary tubes. The 

 spongy cellular tissue, without epidermis, at the tips 

 of roots, is surrounded by moisture, which has de- 

 scended, as rain and dew, through the air and soil, dis- 

 solving, in its passage, the various matters which are 

 the food of plants. Just as the water of your wash- 

 bowl wets the whole towel when a corner has been 



