2l6 



MONOSTROMA, ULVA, AND NITELLA less. 



while some of them undergo a more or less striking differen- 

 tiation according to the position they have to occupy, and 

 the function they have to perform. 



Fig. 48. — Embryo of Chara, an ally of Nitella, showing the ovary 

 {ov}'), from the oosperm in which the embryo has sprung : the two 

 nodes {ftd), apical cell (a/>. c), rhizoids (rA), and leaves (/) of the 

 embryo : and the rudiment of the leafy plant (shaded) ending in the 

 characteristic terminal bud {term, bud), (After Howes, slightly altered.) 



Impregnation takes place in the same manner as in 

 Vaucheria (p. 173). A sperm makes its way down the 

 canal in the chimney-like crown of cells terminating the 

 ovary, and conjugates with the ovum converting it into an 

 oosperm. 



After impregnation the ovary, with the contained oosperm, 

 becomes detached and falls to the bottom, where, after a 



