22 BOl^ANY. 



the nucleolus. The iodine here has killed and stained the 

 protoplasm. 



46. Living protoplasm resists the action of some reagents. — 



If a few living threads are placed in a i$ aqueous solution of 

 eosin, and after a time washed, the protoplasm remains un- 

 colored. This teaches that protoplasm in a living condition 

 resists for a time the action of some reagents. (The iodine 

 and eosin here used are called reagents.) But let us place 

 these threads for a short time, two or three minutes, in strong 

 alcohol, which kills the protoplasm. Then mount them in the 

 eosin solution. The protoplasm now takes the eosin stain. 

 After the protoplasm has been killed the nucleus is no longer 

 elliptical or angular in outline, but is rounded. The strands 

 of protoplasm are no longer in tension as they were when alive. 



Exercise 1 1 . 



47- The alga epirogyra. — Place some of the threads in a shallow vessel 

 of water. Note the appearance of the threads, their length. Determine if 

 branches are present or not. If a small hand lens is convenient, spread some 

 of the threads out between two glass slips, and holding the preparation toward 

 a lighted window look at it through the lens. Describe what is seen. Lift 

 some of the threads with the aid of a needle, and notice how long and delicate 

 they are. Feel of some between the thumb and finger. Pinch some of the 

 threads and again place them in the water. Write an account of the observations. 



Place some threads in a small quantity of alcohol and let remain for 

 several minutes. Does the alcohol become colored green ? Why ? 



Place some of the threads in a solution of iodine for a few moments. Rinse 

 them in water. Do the threads hold the color ? What is the color ? 



Place some fresh threads in a l% solution of eosin for a few moments. Rinse 

 in water. Do the threads hold , the stain ? Why ? Place the same threads 

 for a few moments in strong alcohol, and then in the eosin. Rinse in water. 

 Do the threads now hold the color ? Why ? 



Write out a complete account of your experiments and observations in this 

 study of the gross characters of the ^lant spirogyra. 



