THE PLANT GROUPS 109 



2. Habit. Wash the earth from some moss plants and pre- 



pare them for study. Observe the parts of the plant 



body and compare them with those of higher seed plants. 



a. Plan of the plant body. Is the central axis divided 



into regular nodes and intemodes ? Are there lateral 



and terminal buds ? Are the leaves cyclic or spiral 



in arrangement ? Have the hairlike roots, or rhizoids, 



any definite points of origin on the stem ? Do roots 



and leaves have any definite tropic response ? Sketch 



a stem, using outline figures, to indicate the relation 



of parts of the plant body of the moss. 



b. Study the microscopic structure of the leaves and 



rhizoids and indicate the cellular structure of these 



organs by accurate drawings. 



3. Reproduction. Study plants which have antheridia and 



archegonia in the terminal buds. The males may be 

 recognized as open disks, or clusters of antheridia, ter- 

 minating the stem. The female plants have similar 

 clusters of archegonia borne in closed buds. 

 a. Male disks and antheridia. Cut off the male head and 

 dissect it out in a drop of water on a slide. 



(1) What is the shape of the moss antheridium ? its 



structure ? Is it composed of different cell layers ? 

 How do these layers differ in structure ? What 

 function do you consider that each cell group, 

 or layer, has in the development and liberation 

 of sperms ? Do you find other cell structures 

 among the antheridia ? Sterile cell chains, called 

 paraphyses, exist among the antheridia of most 

 mosses, which probably protect the developing 

 antheridia. 



(2) Draw antheridia and paraphyses. Label the parts of 



the antheridium according to position and function. 



