GREEN ALGAE 



397 



pairs (Fig. 335, i.). In Bryopsis the size is unequal (ii.) ; while Codiwu 

 shows still greater inequality (iii.). This is again more marked in 



Fic. 335- 

 Gametes of vai^ious Siphonales, and Siphouocladiales, illustrating diilerentiation 

 of male and female. i=Acctabidana, isogametes ; W^Bryopfiis ; iu = Codi um( ; 

 \\' — Sphae}OpUa ; v^Vaucheria. In iv. and v. the large egg is stationary, while 

 the smaller spermatozoid is motile. (Taken from Oltmanns' Algiu:.) 



Spliaeroplea, where the large egg is non-motile (iv.), a condition still 

 more accentuated in Vaucheria (v.), which is the most advanced of 

 all in sexual differentiation. 



The sex-organs of Vaucheria arise 

 close together as short lateral branches 

 {V. sessilis), or borne together on the 

 same branch [V . terreslris, Fig. 336). 

 The antheridia are horn-like, curved 

 bodies, the oogonia are oval. In the 

 antheridium a septum cuts off the 

 multi-nucleate protoplast from the 

 parent tube : each nucleus becomes the 

 centre of a spindle-shaped sperma- 

 tozoid ; and these escape, with their 

 paired cilia pointing fore and aft, 

 through an opening at the distal end. 

 The oogonium also at first contains 

 numerous nuclei embedded in proto- 

 nlasm stored with many globules of oil. 



r - ° Fig. 336. 



But, as theOVUm matures, all the nuclei Sexual branch of vaucheria lernslns. 



, , , ■ , . bearing distallv a cur\'ed antheriditim, and 



but one wander back into the parent right and left oval oogonia. 



