DEVELOPMENT OF THE OSTRICH FERN. 21 



jacent cells. The protoplasm in the papilla is dense, especially in the middle, and con- 

 tains small chlorophyll granules. A septum is then formed, by which the jiapilla, now 

 the mother-cell of the antheridium, is shut off. This may be followed by a second wall 

 l^arallel to the first so as to form a pedicel, but this is unusual (Pi. 4, fig. 29, P). Ordi- 

 narily, the first wall to be formed in the mother-cell is funnel-shaped, the base of the fun- 

 nel being upward and the smaller end of the funnel in contact with the wall by which tlie 

 mother-cell was first cut off" (PI. 4, fig. 16). Sometimes this wall is almost flat, or it may 

 be convex downward but not reaching to the base of the antheridium. The second wall 

 (PI. 4, fig. 17) is nearly constant in form, dome-shaped or hemispherical and follows 

 pretty closely the outline of the antheridium which has by this time grown rapidly and 

 become nearly globular in shape. Finally, a third wall is formed in much the same way 

 as the first, and like it subject to considerable variatiop (PI. 4, fig. 18). The cell thus 

 formed is the cap-cell and has its inner surface in contact with the upper part of the second 

 wall. The antheridium now consists of four cells: an inner cell containing dense, finely 

 granular protoplasm, but no chloroi^hyll; and three others which suri-onnd this, in which 

 there is less protoplasm, but some small chlorophyll granules. Of the three outer cells the 

 two lower are thus annular in form, except in cases where the first wall formed is not suffi- 

 ciently convex to touch the basal wall of the antheridium, in which case the lower cell is 

 discoid. About the time the cap-cell is formed, or sometimes before, the central cell be- 

 gins to divide. The first wall (PI. 4, fig. 20) is vertical, dividing the cell into nearly 

 equal parts. This is followed by a second vertical wall (PI. 4, fig. 23) at right angles 

 to the first, so that when the antheridium is seen from above, the cells are ari-anged like 

 quadrants of a circle. These undergo further divisions (PI. 4, fig. 22) until there are 

 about twenty cells. Their form is polyhedral, but the outer walls are rounded so that 

 those on the outside of the mass appear almost globular. The pi-otoplasm is highly re- 

 fractive and finely granular and each cell is provided with a small but evident nucleus. 

 As soon as the sperm cells are fully grown the formation of the antherozoids begins. 

 The protoplasm becomes somewhat more coarsely granular and the nucleus indistinct, 

 though it does not actually disappear and can usually be demonstrated by staining. When 

 it becomes more evident again, it is seen to have changed form and to have increased in 

 size (PI. 4, fig. 25). Instead of being globular, it is now crescent-shaped. It grows 

 larger, becoming at the same time more curved (PI. 4, fig. 26). This continues until it 

 is soon evident that what was the nucleus of the cell is assuming the appearance of the 

 complete antherozoid. Growth continues until the body of the antherozoid is in contact 

 with the wall of the mother-cell, and lies coiled up within it, leaving, however, some 

 remains of the protoplasm of the mother-ceil lying between the coils. When the anthero- 

 zoids are nearly mature, the walls of the sperm cells, which were hitherto in close con- 

 nection, become partially absorbed leaving the sepai'ated sperm-cells free in the cavity of 

 the antheridium. If an antheridium, in which the walls of the sperm-cells have undergone 

 degradation, is placed in water, a very marked movement of the contents of the anthe- 

 ridium may sometimes be observed, dnc apparently to the absor[)tion of water by the mu- 

 cilaginous walls and their breaking down and dissolving through its action. Enough 

 of the wall is left, however, to still enclose the antherozoid. By the time that they are 

 ready to escape, the sperm-cells are so crowded as to press with sufficient force against 



