PELLIA. 321 



460. Antheridium and Archegonium (Figs. 68, 69). 



In sections (transverse and longitudinal) passing through an 

 antheridial cavity, note that the antheridium is nearly 

 spherical, with a very short stalk, and is seated in a flask- 

 like depression in the upper tissue of the thallus, which 

 has grown up over the antheridium but has left a narrow 

 pore at the top ; the antheridium has a single-layered 

 wall, and (unless dehiscence has already occurred) con- 

 tains very numerous small sperm-cells which produce the 

 antherozoids. 



In longitudinal sections passing through an archegonial 

 cavity, note the archegonia, which spring at right angles 

 from the convex vertical hinder end of the cavity and are 

 therefore horizontal in position. In a well-grown arche- 

 gonium, note (1) the short thick stalk ; (2) the dilated 

 venter, containing the spherical oosphere and the ventral 

 canal-cell above it; (3) the long neck, consisting of a 

 single layer of cells and an axial row of neck-canal-cells. 

 Between the archegonia note the short mucilage -hairs or 

 paraphyses, usually two-celled. 



461. L. S. of Sporogonium in situ (Figs. 68, 70). 

 (a) In longitudinal sections through a plant with a nearly 

 ripe'sporogonium, note (1) the tissues of the thallus ; 



(2) the unfertilised archegonia and the paraphyses, 



at the posterior end of the cavity and around the base of 



(3) the calyptra or enlarged venter of the fertilised 

 archegonium, which is several cells thick and bears the 

 withered neck near its apex ; (4) the sporogonium, 

 covered anteriorly by the calyptra and projecting posterior- 

 ly into the thallus tissue. 



(6) In the sporogonium itself, note (1) the seta, 

 consisting of regular longitudinal rows of very short cells 

 filled with small starch-grains test with iodine ; (2) the 

 foot or haustorium, conical in form and having its edge 

 produced around the base of the seta like a collar thus 

 increasing the surface for absorption from the thallus- 

 tissue ; (3) the capsule, nearly spherical. 



(c) In the capsule note (1) the outer wall layer, 

 P.B. 21 



