xiv] 



THE ANTHERIDIUM 



287 



the intruding cells of the wall projecting inwards further than the ring of 

 attachment of the cap-cell {r, Fig. 277, d, e). 



The antheridia of the Eusporangiate Ferns differ widely from those of 

 the Leptosporangiate type. They are more massive, and are deeply sunk 

 in the tissue of the prothallus. The very numerous spermatocytes which 

 they contain are covered in by a wall of which certain of the cells divide 

 periclinally: but one, or sometimes more, may remain undivided, and act as 

 an opercular cell (or cells). (Figs. 278, 283, A.) A layer of slab-like cells 

 cut off from the adjoining tissue of the prothallus sometimes surrounds the 

 mass of spermatocytes, and is nutritive in function like a tapetum. Later 

 these cells assist in the extrusion of the spermatocytes by swelling into the 

 antheridial cavity. 



Fig. 277. Antheridia of fFw^^i'a //z'^wj/.r, after Schlumberger. a = antheridium 

 with spermatocytes ; ^^ripe antheridium with cuticle ruptured ; c, rt'=same 

 antheridium before and after dehiscence; f = lateral and vertical aspects of 

 ruptured antheridium. f = cuticle; o = opercular cell; r = ring-cells. 



The archegonium of Ferns has its ventral region sunk in the tissue of 

 the prothallus. Sometimes even the neck may also be so far embedded that 

 it projects only slightly beyond the surface, as in Marattia Doiiglasii, or 

 Ophioglossuni pendidmn (Fig. 278, c, d,f). But usually the neck projects as 

 a cylindrical chimney composed of four rows of cells, the number of cells in 

 each row being variable in different Ferns. The central series as seen in 

 Dryopteris holds with remarkable constancy for Ferns at large (Fig. 279). 

 It consists of the canal-cell with two nuclei, the ventral-canal-cell, and the 

 ovum. There may be some slight difference whether or not the division of 

 the canal-cell into two is completed, or the division be confined to the 

 nucleus only. Otherwise the central series of cells of the archegonium in 

 Ferns seems to have settled down to a structure which so fully meets the 



