18 PRACTICAL BOTANY. 



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 sporogonium, with its rounded head, 

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



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

 nexion with the foot of the sporogonium, and is continuous 

 upwards into 



4. 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 collimella, 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 to 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. 



