114 REPRESENTATIVE PLANTS 



How do tlie whorls compare in the length of branches as 

 you approach the top or tijj of the axis? The very tip 

 looks like a bud and is called the apical hud. The branches 

 arise from the nodes and that part of the axis between two 

 consecutive nodes is called an internode. How do these 

 compare in length from end to end? 



Structure. Examine a branch (Ip) and study the nodes 

 and internodes. How many branches at each node? What 

 do you observe on looking at the branch surface? Look 

 now at the surface of the main axis, and observe the similar- 

 ity of each to the other. You ought to see elongated cells 

 more or less spirally arranged. Examine a branchlet for cell 

 structure. The cells noted above in the main axis and 

 branch are called cortical cells. 



Reproductive bodies. In material having gamete bodies 

 observe on a branch, at each node, two forms of reproduc- 

 tive structures, the female gamete (oosphere or oogonium) 

 above, and the male gamete (antheridium) below the branch- 

 lets. How do these differ from each other in form, size, 

 color, and markings? 



Observe the oosphere more attentively, and find, if possi- 

 ble, spiral cells on the outside, and a large central cell 

 within (oospore), also a lobed margin or mouth. Crush 

 an antheridium and observe the plates composing it, also 

 the strange jointed filaments or sperms (those under water 

 move about, some entering into and uniting with the oosphere 

 to produce the oospore). The oospore, on germination, 

 produces a new plant. 



Section of stem. Study a section of the axis (Ip)) and ob- 

 serve a large central internodcd cell and a layer of outside 

 cortical cells. Compare with the parts of the oogonium. 



Drawings. Draw a plant, natural size, with the details, 

 showing a node, branches, branchlets, parts of the adjacent 

 internodes, and a cross section of the axis (/jv). Also a fertile 

 branch bearing the antheridia and the oogonia, and details 



