MOSSES AND LIVERWORTS (BRYOPHYTES) 261 



One of the sex organs, the archegonium', is flask-like, the neck 

 being greatly elongated (Fig. 217, A and B). In the swollen 

 part of the archegonium the female gamete or egg is formed. 

 When the egg is mature the central cells in the neck disor- 

 ganize and the tip of the neck opens, 

 thus leaving a, gelatinous passage- 

 way into the open end of the arche- 

 gonium and through the neck to 

 the egg. The other sex organ, the 

 antheridium, is club-shaped (Fig. 

 218), being attached by its smaller 

 end to the end of the stem. Within 

 each antheridium thousands of male 

 gametes or sperm cells form. When 

 abundant moisture is present (dew 

 or rain) the antheridium swells, its 

 tip bursts open, and the contents 

 escape. The biciliate sperms swim 

 about actively, and if some of them 

 come into the vicinity of the arche- 

 gonium neck they make their way 

 down through the gelatinous pas- 

 sageway. One of the sperms unites 

 with the egg, thus producing the 

 oospore. It is evident that the diffi- 

 culty of securing fertilization of the 

 egg in this case is greater than in 

 such plants as VaucTieria and (Edogo- 

 nium. But the very large number of 

 sperms produced in moss antheridia 

 helps to make it possible for sperms 

 to be widely spread, thus making fertilization more probable. 



245. The moss plant : the oospore and its product. The 

 oospore begins to grow almost as soon as formed. It grows 

 from the place in which it was formed, and soon elongates 

 and thickens until its lower end pushs down into the end of 



FIG. 218 



An antheridium (a) of a moss. 

 From its tip the sperms (&) are 

 escaping, and one of them is 

 shown enlarged at the side (c). 

 a and 6, magnified 350 times; 

 c, magnified 800 times. After 

 Sachs 



