SPHAGNUM 359 



If specimens of the sporogonia be at hand, note with the 

 naked eye 



1. The spherical form of the sporogoniura. 



2. Its position, seated on the end of a more or less elongated 

 stalk the pseudopodium : this must not be confounded with 

 the seta of other Mosses ; as sections will show, the true seta in 

 Sphagnum is short, and the pseudopodium is merely a prolongation 

 of the axis of the oophyte generation. 



3. The calyptra, which may be, according to age, a more or 

 less complete covering of the sporogonium, and is derived from 

 the wall of the archegonium. 



4. Where the calyptra has been broken away or removed, the 

 circular lid-like operculum may be seen at the apex. 



Cut longitudinal sections of the sporogonium : mount in 

 glycerine or glycerine-jelly, and, selecting those which are 

 median, examine under a low power 



1. The outline of the sporogoniuni, with its rounded head 

 and short seta, enlarged at its base into a broad foot. 



2. The pseudopodium, which is in close physiological con- 

 nection with the foot of the sporogonium, and is continuous 

 upwards into 



3. The calyptra, which may be seen, according to age, more 

 or less completely enveloping the sporogonium. 



Turning to the internal structure of the sporogonium, 

 observe 



1. The central, massive columella, consisting of thin- walled 

 cells : it is rounded off at its apex. 



2. The spore-forming layer, which appears semilunar in 

 section, being in reality of a bell-shape : according t.o the age 

 of the sporogonium, spores of various stages of development may 

 be seen composing the spore-forming layer. 



3. Outside this is the wall of the sporogonium, consisting of 

 some three or four layers of thin- walled cells, enveloped by a 

 single layer of cells with thick brown walls. In this layer note 

 towards the apex two points where the cells are smaller : here 

 the section has traversed the circular line of rupture of the 

 operculum. There is no peristome. 



