594 '^^E AMERICAN NATURALIST. [Vol. XXXVIII. 



The angiosperms present no especial advance over Gnetum in 

 the organization of the egg except that this structure is generally- 

 reduced to a single female nucleus and the cytoplasm immedi- 

 ately around it (see Fig. \i d). This egg nucleus flanked by 

 two companions (synergids) and the accompanying protoplasm 

 compose the &g^ apparatus whose morphology is still a matter 

 of dispute. It is possible that the synergids may stand for 

 portions of a reduced archegonium, but the two nuclei bear such 

 close relations to the egg and polar nucleus that it seems very 

 probable that they are homologous with these structures which 

 have clearly defined sexual potentialities. In spite of the 

 numerous studies on embryo sacs in various groups of angio- 

 sperms we do not yet know precisely how the cytoplasm becomes 

 gathered around the egg nucleus and the synergids. The 

 spindles that are formed between these nuclei in some types 

 (e. g., Lilium) have been supposed to lay down walls by means 

 of cell plates. But there are other forms in which the proto- 

 plasm seems to separate along planes of vacuoles without rela- 

 tion to spindle fibers. 



( To be continued.^ 



