378 PRACTICAL BOTANY 



the structure of the cells of the wall : the outer 

 layer have soft cell-walls, the inner firm and 

 dark-coloured walls, an arrangement which 

 will result in the opening of the sporogonium 

 on drying. 



The spores are not simple cells, but undergo division of the 

 contents before they are shed. 



It will be well also to compare the sporogonium of Anthoceros, 

 noting the foliaceous irregularly-branched thallus, the upright, 

 elongated, and cylindrical sporogonia, which are inserted on the 

 upper surface of the thallus, and are surrounded at the base by a 

 sheath. The oldest sporogonia may have begun to split into two 

 equal halves from the apex downwards. 



Cut median longitudinal sections of a sporogonium of medium 

 age, and observe the enlarged foot with hair-like outgrowths pene- 

 trating the tissue of the oophyte : the zone of basifugal inter- 

 calary growth immediately above this : the capsule above will 

 be seen to consist of a wall four or five layers of cells in thickness, 

 and having stomata ; a sporogenic layer, in which the division 

 of the cells into four may be easily recognised : and a thin central 

 eolumella. Transverse sections will show that the wall is 

 thinner at two points than elsewhere, and it is here that the 

 rupture takes place when the sporogonium matures. 



