and Laboratory Methods. '^'iS? 



Laboratory Outlines for the Elementary Study of Plant 



Structures and Functions from the Standpoint 



of Evolution. 



XXVIII. Cham Sp. 



Class and order, Charales. Family, Characeae. Stoneworts. 



The stoneworts are algae which are found growing in the bottom of ponds, 

 lakes, or slowly flowing creeks and rivers. They are of considerable size and 

 are usually covered with an incrustation of lime. They contain numerous branches 

 arranged in whorls and are firmly fixed in the mud by means of rhizoids. 

 Charas grow very readily in an aquarium and may be kept in a healthy condi- 

 tion all winter by simply placing the plants into a glass jar of water and keeping 

 them near a south window. 



1. Sketch an entire plant and describe the naked eye characters. Notice 

 the odor, the nodes and internodes, and the brittleness of the filaments. 



"2. Mount the base of a plant in water and examine under low power. 

 Draw and describe some of the branching rhizoids. Study the rotation of the 

 protoplasm under high power. 



3. Mount the terminal part of a young branch, being careful so as not to 

 crush the brittle lateral branches. Examine under low powder and draw the ter- 

 minal bud. Notice the great internodal cells covered with a cortical layer and 

 the whorls of lateral branches. 



4. Draw a cell of one of the branches without a cortical layer, showing the 

 incrustation of lime. 



5. Under high power draw part of a cell, showing the chloroplasts. How 

 are they arranged? Draw several in stages of division. How do they divide? 



6. Study the rotation of the cytoplasm in the large cells of the branches and 

 describe. How does it differ from that in the cells of Philotria ? Why are the 

 chloroplasts arranged in rows? Note the movements in opposite directions on 

 either side of the neutral line. Is the direction of rotation the same in all the 

 cells ? 



7. How is the cortical layer developed ? In order to determine this, young 

 branches should be observed. Draw a cross section of the main stem. Note 

 the short projecting cells which roughen the surface. 



>>. The sexual organs are produced during summer and autumn. Study 

 fresh material, or if this is not at hand, material preserved in alcohol or Petit's 

 solution. The antheridia and oogonia are situated on the lateral branches. 

 Draw. Notice the five spiral branches which cover the oogonium. How does 

 this oogonium difter from that of Vaucheria? The antheridia are globular 

 organs which are red in color when fresh. Is this plant hermaphodite or uni- 

 sexual ? 



9. Draw an oogonium containing a ripe oospore. Explain the structure of 

 the entire body. 



