136 REPRESENTATIVE PLANTS 



This, in germinating, becomes the structure studied in the 

 next paragraph. 



The sporophyte. Study a complete moss {i.e. one with a 

 leafy stem, capped by a naked stalk, bearing an enlargement 

 at its summit) and observe the two structures mentioned. 

 The stalk is the pedicel or seta and the enlargement is the 

 capsule, often called the fruit. What is the color, size, and 

 length of the seta ? If possible, observe a young specimen. 

 In this case what do you observe inclosing the enlarged 

 end ? Study now a full-grown seta and capsule. What is 

 the shape, size, color, and appearance of all the visible 

 parts of the latter (m)? A pointed or conical sheath or 

 cover, fitting snugly over the end, is the calyptra. Remove 

 by the fingers and observe beneath, and covered by it, a 

 conical or hemispherical, pointed lid, the operculum, separ- 

 ated from the capsule proper by a seam. Remove the oper* 

 culum, and some fine teeth, the ijeristome, may often appear, 

 surrounding the mouth of the capsule, and showing in some 

 cases in their midst the protruding sporangium. Apply 

 pressure Qp) and rupture a capsule, and observe the spores. 

 Are these large or small ? Are they few or many ? What 

 shape and color have they ? What use has each structure 

 mentioned above ? 



Life history. You have discovered in your study of the 

 moss that there are two different plants, each arising from 

 a spore, but intimately connected. This condition is called 

 the alternation of generations. Generation I was the leaf- 

 bearing gametophyte — coming from a si)ore formed in the 

 capsule. Generation II, consisting of the naked seta and 

 the capsule, is called a sporophyte, and grew from the spore 

 lodged at the summit of the female gametophyte. How do 

 these generations differ in ability to live independent lives ? 

 Which one can be considered a parasite ? What benefit is 

 it to the moss to have its capsule elevated ? 



Moss problems. Thoroughly dry freshly gathered moss 



