DISTKIBUTIOX OF SPOKES AXD SEEDS. 



355 



stalk, so that it is surrounded by a mass of mucilage, thus 

 enabling it to adhere to any object which it strikes. 



Filaments carrying the spores often twist upon drying 

 and thus jerk oft" the spores as they suddenly slip past some 

 obstruction, ^\'hen spores are produced in chains, either 

 the walls of a special cell or a layer of the cell-wall between 

 them may act as a separator 1)V its alteration into mucilage 

 (-■J, fig. 399). In some cases the spores are wedged apart by 

 the secretion, between the la}"ers of the wall joining them, of 

 a cellulose plug which gradually elongates into a slender 

 spindle to whose tips the spores are so slightly attached that 

 the lightest breath carries them away {B, fig. 399). The 

 elaters of the li\er\vorts (fig. 11 and *' 321) serve in some 

 cases to sling out the spores when the capsule bursts ; in other 

 cases, as in Marchanlia, they entangle the spores, insuring 

 gradual and preventing too sparing distribution. The teeth 

 around the mouth of the capsule of mosses serve to distribute 

 the spores at opportune intervals, instead of ha\ing them 

 emptied out all at once. In some mosses the teeth are erect 

 or recurved when dry, but upon being moistened they arch 

 over the mouth, thus 

 forming a nearly closed 

 cover (fig. 400). Others 

 have the teeth arched 

 over the mouth when 

 drv or permanentlv fas- 

 tened together by their 

 tips, thus narrowing the 

 opening and allowing 

 the spores to sift out 

 between them. In some 

 cases the teeth, by their 

 form and hygroscopic curvatures, serve to sling out the spores 

 to a short distance. In many ferns the annulus of the spo- 



FlG. 400. - Capsules <if a muss {(.i7i7>u)i la) after 

 fall of lid. A , teeth erect when dry. lea\"ing cap- 

 sule widely open ; S. the same in damp weather. 

 Magnified about lo diam. — After Kemer. 



