18 Transactions. 



others the outer, is the larger. The mother cell does not at first project 

 beyond the surface of the prothallus, but by the time the first division in 

 it has taken place it has enlarged considerably and has begun to project 

 noticeably. The next division takes place in the outer cell by an anti- 

 clinal wall (figs 24, 25). I have no direct information as to the exact 

 sequence of divisions which takes place in the cover-cell, but it is clear 

 that it gives rise to the whole of the outer free wall of the antheridium, 

 whilst from the inner cell is formed the mass of spermatocytes. From 

 figs. 26 and 28 it would seem that a good deal of segmentation takes place 

 in the inner part of the developing antheridium before the outer wall 

 begins to project at all strongly. I did not observe in my preparations 

 any instances of an antheridium in this stage in transverse section, but 

 it will probably be the case that quadrant and octant divisions are formed 

 in the inner cell, as is known in other Pteridophytes. The free wall of 

 the antheridium is never more than one cell in thickness. The mature 

 antheridium projects very strongly beyond the surface of the prothallus as 

 a hemispherical globular body, the number of cells in the free wall being 

 large. From mature antheridia seen in surface view (fig. 14), it is evi- 

 dent that the division walls in the cover of the antheridium intersect 

 one another more or less at right angles, so that the opercular cell is four- 

 sided. This cell is situated at the apex of the antheridium, and is first 

 to be distinguished in surface view by its walls becoming brown in colour 

 (fig. 14). This browning later extends to the adjacent cell-walls, and, 

 before the antheridium has discharged, both walls and contents of most 

 of the cover-cells in the exposed portion of the antheridium have assumed 

 the same coloration. The interior cells of the antheridium rapidly sub- 

 divide (figs. 29 to 33), so that a large number of spermatocytes is formed, 

 although the number is not so great as in certain of the Ophioglossaceae 

 and in the subterranean types of Lycopodium prothalli. From the adjacent 

 prothallial cells a wall of more or less flat cells is cut off surrounding the 

 lower portion of the antheridium. The opercular cell seems to vary in 

 size for different antheridia. Rupture of the antheridium is initiated by 

 the disorganization of this cell, while in still older antheridia it is generally 

 to be observed that the cells of the outer wall which adjoin this aperture 

 have also broken down, so that the characteristic appearance of the 

 numerous old discharged antheridia on the main prothallus body is that 

 of small brown saucer-like structures projecting from the surface. The 

 details in the formation of the sperms were not followed. I was unsuc- 

 cessful in my endeavour to make the sperms swarm in fresh prothallial 

 sections, and the method of staining was not suitable for showing the details 

 of spermatogenesis. Possibly, also, a better killing and fixing solution would 

 have to be sought for this purpose. 



The earliest stages in the development of the archegonium are to be 

 distinguished by the very large size of the nucleus in the inner cell. As 

 in the young antheridium, the first wall to be formed is a periclinal by 

 which an outer is cut off from an inner cell. The outer or neck cell divides 

 next by an anticlinal wall (figs. 35, 36), a surface view showing that 

 two such walls are quickly formed intersecting at right angles, so that 

 the archegonium neck-cells have the usual quadrant form (fig. 15). These 

 four cells give rise to the neck of the archegonium, and soon project sharply 

 beyond the surrounding epidermal cells (figs. 36 to 38, and 40). My 

 preparations show that up to this point the inner cell has not divided, 

 but has merely pushed up slightly between the neck-cells along with the 



