MOSSES AND LIVERWORTS (BRYOPHYTES; 261 







w^ 







One of the sex organs, the archef/onium, is flask-hke, 1he neck 

 being greatly elongaierl (Fig. 217, J and JJ). In tlie swollen 

 part of the arclie^onium 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 

 anthericl ium, 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 &gg, 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 Vaucheria and CEdogo- 

 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 ai 



Fig. 218 



An antheridium (a) of a moss. 

 From its tip tlie sperms (b) are 

 escaping, and one of tliem is 

 sliown enlarged at the side (c). 

 a and 6, magnified 350 times; 

 c, magnified 800 times. After 

 Sachs 



