156 THE NATURE AND WORK OF PLANTS 



a large size, although they may grow rapidly. If well 

 nourished, each nucleus quickly divides into two nuclei. 

 (Nii'cle I is the plural of iiii'cle us.) A new wall appears 

 between these nuclei, forming them into two cells. When 

 either of these has enlarged to the size of its parent, it is 

 ready to divide again, and so on. When we speak of 

 plants growing, we mean that their cells are multiplying 

 in this way. 



Cells take in food through their surfaces, and the 

 amount of food that can enter them depends in part on 

 the extent of their surfaces. Just as a pea has a greater 

 surface in comparison to its bulk than an orange has, so a 

 small cell has more feeding surface relatively .to its needs 

 than a large one has. This means that the larger cells 

 become, the greater their chances of starving. Cell mul- 

 tiplication, then, is a means of saving the life of plants, as 

 well as a process of growth. 



106. Plants as Storehouses of Food. Every plant has 

 some part which it uses for a storehouse. Plants do not 

 use up for their own growth all the food that they gather. 

 They do so for a while, it is true, until they secure a sea- 

 son's growth. Then they begin to store up the plant 

 food in seeds or roots or tubers for their offspring the 

 next season. The farmer takes this stored-up food for his 

 own purposes, just as a bee farmer takes the food his bees 

 have stored away. 



Food stored in the plant always contains both albumen 

 (protein) and starch, but different plants store these things 

 in very different proportions. Some, like beans, are rich 

 in albumen ; others, like corn, in starch. Albumen is the 

 tissue-building part. Starch furnishes heat, or energy. 

 The albuminous foods, or proteins, contain nitrogen (Chap- 

 ter VIII); the starch is carbon, hydrogen, and oxygen. 

 It is called a carbohydrate. Another carbohydrate is 



