154 



FUNDAMENTALS OF CYTOLOGY 



The mature sperm, which straightens out considerably after escape from 

 the antheridium, commonly shows three main parts: (1) a long and slender 

 body representing the condensed nucleus chiefly; (2) a small specialized 

 anterior region composed of the apical body, a small amount of cytoplasm, 

 and the blepharoplast which bears the two cilia, often at different points ; 

 and (3) a residual mass of cytoplasm at the posterior end. 



Fig. 112. — Spermiogenesis in a moss {Polytrichum) . A—D, mitosis in speiinatogenous 

 cells, showing aspect of plastid substance (A;). E-H, last mitosis in antheridium, showing 

 behavior of centrosome, which in each spermatid becomes a blepharoplast (6). I~L, trans- 

 formation of spermatid into biciliate spermatozoid: a, apical body; /, limosphere; n, nucleus. 

 {After C. E. Allen.) 



The details of syngamy in bryophytes are best known in certain genera 

 of liverworts. The behavior of the motor elements during the process is 

 somewhat uncertain, although it probably parallels that reported for 

 ferns. The nuclear behavior has been closely followed, and it may not 

 be precisely the same in different cases. In Riccardia (Fig. 113) the 

 elongate body of the sperm, consisting of the nucleus and possibly a 

 covering of nonnuclear material, applies itself throughout its whole 



