A HAY INFUSION 



97 



containing a nucleus. It is surrounded by a wall of a woody 

 material formed by the activity of the living matter within the cell. 

 It also contains a lobed mass of protoplasm which is colored 

 green, the chloroplast. Such 

 is a simple plant cell. 



A Hay Infusion. — An ex- 

 ample of the close relation 

 between plants and animals 

 may be seen in the study of a 

 hay infusion. If we place a 

 wisp of hay or straw in a 

 small glass jar nearly full of 

 water, and leave it for a few 

 days in a warm room, certain 

 changes are seen to take place 

 in the contents of the jar : The water gets cloudy and darker in 

 color, and a scum appears on the surface. If some of this scum 

 is examined under the compound microscope, it will be found to 

 consist almost entirely of bacteria. These bacteria aid in the 

 decay which, as the unpleasant odor from the jar testifies, is be- 



A spherkdl digs 



Pleurococcus. This one-celled green plant 

 may live singly or in groups. 



Bacfer/a 



A psramecJum 



Life in a late stage of a hay infusion. 



ginning to take place. Bacteria flourish wherever the food supply 

 is abundant. The water within the jar has come to contain much 

 of the food material which was once within the leaf of grass, — 

 organic nutrients, starch, sugar, and proteins, formed in the leaf 

 by the action of the sun on the chlorophyll of the leaf, and now 

 released into the water by the breaking down of the walls of the 



