484 Mr. VauentineE on the Theca, and on the Sexes of Mosses. 
Fig. 19. A section of the ripe theca of Polytrichum aloides, showing the 4 longi- . 
tudinal inflexions of the columellar membrane and the quadrangu- 
lar columella. 'The columella resembles a Maltese cross, and has 
an axis of dense tissue. The empty space between the columella 
and columellar membrane is occupied by the sporules. 
