ANALYSIS OF PLANT SUBSTANCE. 79 



3. Rough Analysis of Plant Substance. 



162. Some simple experiments to indicate the nature of plant substance. 



After these building-up processes of the plant, it is instructive to perform 

 some simple experiments which indicate roughly the nature of the plant 

 substance, and serve to show how it can be separated into other substances, 

 some of them being reduced to the form in which they existed when the 

 plant took them as food. For exact experiments and results it would be 

 necessary to make chemical analyses. 



163. The water in the plant. Take fresh leaves or leafy shoots or other 

 fresh plant parts. Weigh. Permit them to remain in a dry room until 

 they are what we call "dry." Now weigh. The plants have lost weight, 

 and from what we have learned in studies of transpiration this loss in weight 

 we know to result from the loss of water from the plant. 



164. The dry plant material contains water. Take air-dry leaves, shav- 

 ings, or other dry parts of plants. Place them in a test tube. With a 

 holder rest the tube in a nearly horizontal position, with the bottom of the 

 tube in the flame of a Bunsen burner. Very soon, before the plant parts 

 begin to "burn," note that moisture is accumulating on the inner sxirface 

 of the test tube. This is water driven off which could not escape by drying 

 in air, without the addition of artificial heat, and is called "hygroscopic 

 water." 



165. Water formed on burning the dry plant material. Light a soft-pine 

 or bass-wood splinter. Hold a thistle tube in one hand with the bulb down- 

 ward and above the flame of the splinter. Carbon will be deposited over 

 the inner surface of the bulb. After a time hold the tube toward the win- 

 dow and look through it above the carbon. Drops of water have accumu- 

 lated on the inside of the tube. This water is formed by the rearrangement 

 of some of the hydrogen and oxygen, which is set free by the burning of 

 the plant material, where they were combined with carbon, as in the cellu- 

 lose, and with other elements. 



166. Formation of charcoal by burning. Take dried leaves, and shav- 

 ings from some soft wood. Place in a porcelain crucible, and cover about 

 3 cm. deep with dry fine earth. Place the crucible in the flame of a Bun- 

 sen burner and let it remain for about fifteen minutes. Remove and empty 

 the contents. If the flame was hot the plant material will be reduced to a 

 good quality of charcoal. The charcoal consists largely of carbon. 



167. The ash of the plant. Place in the porcelain crucible dried leaves 

 and shavings as before. Do not cover with earth. Place the crucible in 

 the flame of the Bunsen burner, and for a moment place on the porcelain 

 cover; then remove the cover, and note the moisture on the under surface 

 from the escaping water. Permit the plant material to burn; it may even 

 flame for a time. In the course of fifteen minutes it is reduced to a whitish 



