294 HOFHKISTER, ON 



phyll vesicles arc spread over their inner wall. The me- 

 dian cavity of the cell is filled with a watery fluid. The 

 axile cells of the young antheridimn form an oval group, 

 composed of four longitudinal rows of cells, and contain 

 finely-granular mucilage (PL XXXVII, fig. 24). By 

 rapidly repeated division in all three directions of space 

 they are transformed into a mass of small tessellated cells, 

 which at first are in very close connexion with one another. 

 In each of them a flattened ellipsoidal cellule is formed 

 (PI. XXXVII, fig. 25), in the interior of which a small 

 vesicle with less highly refractive fluid contents is some- 

 times visible (PL XXXVII, fig. 26). The waUs of the 

 firmly adherent cubical cells are now dissolved, and the 

 ellipsoidal cellules become free. A gelatinous mass, spread 

 over their inner wall, soon begins to be visible ; it forms 

 an imperfect ring parallel to the major axis of the ellipsoidal 

 cell. - This is the first indication of the nascent sperma- 

 tozoa (PL XXXVII, fig. 27). Numerous mucilaginous 

 granules remain for a long period in the middle point 

 of the cellule, even until the ripening of the antheridium. 



The apical cells of the covering layer of the antheri- 

 dium, which are usually eight in number, contain little or 

 no chlorophyll. In the elongated antheridia of Eq. limosum 

 the cells adjoining these apical cells have also very little 

 chlorophyll (PL XXXVII, fig. 24). When the organ is 

 ripe the apical cells part asunder, and the cellules enclosing 

 the spermatozoa ooze slowly out. 



These cellules are larger in Equisetum than in any other 

 known plant. In Eq. arvense their diameter attains ^' l . 

 When the vesicle is ripe the spermatozoon soon becomes 

 partly free, apparently by the distension and dissolution of 

 parts of the wall of the enveloping cell. The numerous cilia 

 on its thick fore-end commence their active oscillating motion, 

 by means of which the spermatozoon with the attached 

 vesicle moves rapidly about in the water on the slide. The 

 spermatozoon seldom becomes entirely free from its mother- 

 cell. When it does so, it has the form of a spiral vermiform 

 body, consisting of a mucilagino-gelatinous substance be- 

 coming dark-brov/n under iodine. Its fore-end, which is 

 the thicker of the two and slightly compressed laterally, 



