CHAPTER V. 



THE PLANT. 



A BRIEF account of the f anctions of the various parts of a 

 plant will be given in this chapter, followed by a short de- 

 scription of the chief chemical compounds existing as its 

 constituents. For detailed accounts of the structure and life- 

 history of plants a treatise on botany wOuld naturally be 

 consulted. 



Germination. — A seed is essentially a germ, with a store 

 of material, out of which the future plant is to be formed. 

 All seeds contain complex nitrogenous compounds (proteids) 

 and either cai-bohydi-ates or fats, together with mineral 

 matter. 



Seeds may be kept unchanged for some time, provided they 

 be protected from moisture. In order that germination may 

 occur, the access of moisture and oxygen, a suitable tempera- 

 ture, and the removal of evolved carbon dioxide are necessary. 

 If these conditions are complied with, seeds will germinate 

 readily without requiring any mineral or other food. Oxygen 

 is absorbed, heat is produced and carbon dioxide is evolved. 



Unorganised ferments, or enzymes — i.e., substances which 

 are soluble in water, and which have the power of bringing 

 about chemical changes apparently without themselves being 

 altered — are produced, and the starch or other insoluble con- 

 stituents of the seed are converted by the enzymes into sugars 

 or other soluble compounds capable of being transported to 

 the pluinule (the rudiment of the stem) and radicle (eventually 



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