484 Mr. Valentine on the Theca, and on the Sexes of Mosses. 



Fi"-. 19. A section of the ripe theca of Polytrichum aloides, showing the 4 longi- 

 tudinal intiexions 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. 



