8 2 COMMON LI VER WOR T. 



not so evident as in the other case, and the number of 

 rays is even and not odd, the latter being the result of 

 the growing point being at the ends of the rays, instead 

 of at the sinuses. The various correlated changes can 

 readily be worked out by the student. 



It now remains to account for the position of the 

 two kinds of organs, one being on the upper surface 

 and the other on the lower. We must know in the 

 first place that the antheridia are modified hairs, which 

 originally started on the surface, but became inclosed 

 in cavities by the surrounding tissues growing up about 

 them. They evidently belong to the upper surface 

 from their position, and the fact that those nearest the 

 growing edge are the youngest. In the female inflor- 

 escence we find that the organs nearest the edge are 

 not the youngest, but the oldest. We can only explain 

 this by supposing that they belong to the upper sur- 

 face, but are brought below by the turning under of 

 the growing point. 16 The perichaetium is the thin ex- 

 panded edge of the thallus. 



The antheridia and archegonia originate, as in the 

 case of the gemmae, from papilliform hairs, which divide 

 into two cells by a transverse wall, the lower cell becom- 

 ing the pedicel, and the upper the body of the organ. 17 

 Paraphyses, which are always sterile bodies, are very 

 common among the cryptogams; their significance is 

 not understood. 



The antherozoids may be taken as the type of the 

 motile male element in fertilization. They are formed 



16 Strasburger, Das botanische Practicum, p. 439; Leitgeb, Unter- 

 suchungen liber die Lebermoose, vi, 1881. 



17 Sachs, Text-book, 2nd Eng. ed., p. 348. 



