37 2 APPENDIX. 



7. Hold a bit of the main axis (use decalcified plants) between 

 the halves of a piece of pith and with a very sharp knife or a 

 razor cut a transverse section of the axis. Mount on a slide in 

 water with cover glass, and examine with lens. Observe the 

 central cell, surrounded by a row of cortical cells. (Fig. 37.) 



8. Trace the course of the rows of cortical cells by examining 

 the surface of the axis with lens. Note the short projecting cells 

 which roughen the surface. (^[ 35.) 



9. Demonstration. If fresh material is available mount a living 

 rhizoid in water and show the rotation of the lumpy protoplasm. 



10. On the lower whorled branches observe the black ovoid 

 resting spores, surrounded by a paler cortex, with a crown of five 

 cells at the free end. Study these on successively higher and 

 higher branches, and observe differences in color, and finally of 

 shape. What is the form of the youngest (ovary) ? (^[ 389, fig. 



3I3-) 



11. Examine at the same time the spherical spermaries (orange 



or scarlet in fresh specimens) which are found with some ovaries. 

 Why are they absent on older branches ? Can any trace of them 

 be found? (If 383, fig. 313.) 



12. Demonstration. Mount young ovaries and show the central 

 cylindric egg; the five cortical cells, straight in the youngest, 

 spirally twisted in older ones, terminated by five crown cells, 

 between which the sperms make their way to the egg. 



Mount entire spermary; also on another slide one teased out 

 with needles ; show the eight wall cells, united by zigzag edges, 

 each carrying a handle-cell on its inner face, from which arise 

 numerous filaments composed of disk-like cells each containing 

 one sperm. 



G. POLYSIPHONIA (P. variegata}. 



Place a plant in a glass dish over a black or white background. 

 Observe 



1. The form of the body and the mode of branching. (Fig. 39.) 



2. The mode of attachment at the base, if specimens are entire. 



3. Demonstration. Mount the tip of one of the branches and 

 show the high, dome-shaped apical cell, with segments cut off 

 successively from its base, to be later themselves divided 

 longitudinally. (If 39, fig. 41.) 



4. Cut a transverse section of a medium sized axis and observe 

 the four large peripheral cells, surrounding a central cell; the 

 latter to be seen only under compound microscope. (^[ 38, fig. 40.) 



