A MANUAL OF BOTANY 135 



Parts and structure. Kxaminn tlu^ leafy specimens fur- 

 nished (naked eye and in). 



Observe the central stem, bearing the leaves. Are the 

 latter few or many ? Are they large or small ? Why are 

 you inclined to call them leaves ? What, in your own words, 

 is a leaf? Compare leaves of different mosses for size and 

 shape. Mount a stem with some fresh green leaves and 

 study (Ip). Observe the leaf margin and the presence or 

 absence of veins. Does a leaf appear to you to be thin or 

 thick ? Observe the cell structure of the leaf and the cell 

 chloroplasts. Examine the leaf for stomates. Why are they 

 absent? Examine the lower end of a moss stem for the 

 rhizoids. What color have they ? Are they branched or 

 not ? Carefully observe a large one and find out whether it 

 is a one or more than one-celled structure. What may be 

 the use of the rhizoids? Study a cross section of a moss 

 stem (Ip) and observe the cell arrangement. Why do we 

 call the structure a stem? (This is the first correct use 

 of the term.) 



The Gametophyte or leafy plant. Compare the stems and 

 leaves of a number of mosses. Examine leafy moss plants, 

 showing the gamete structures at the summit, and possibly 

 a green algalike filament Protonema at the base. These 

 plants are gametophytes, and differ from each other in the 

 arrangement of the topmost leaves. In the male gameto- 

 phyte plant, designated by $ , they form a complete rosette, 

 in the midst of which the antheridia are borne ; in the female 

 gametophyte, designated $ , the leaves are in a cluster more 

 or less closely inclosing the archegonium. If preparations 

 are furnished, study the archegonia and antheridia, or ex- 

 amine carefully good figures of the same found in your text- 

 books. In either case endeavor to fix in your mind tliat the 

 fiask-sha])ed antheridium produces motilp sperms, which in 

 water find their way through the neck of the archegonium 

 into the oosphere, which thus becomes a spore (o()S[)ore). 



