MOSS. SPOROPHORE. 13 



4. A layer of cells with peculiar yellow or brown 

 thickening of the walls : this gives rise to the 

 peristome. 



Returning to the spore-forming layer, it may be 

 verified under a high power 



i. That it consists at first of a single layer of cells 

 (the archesporium) : to ascertain this for certain it 

 may be necessary to cut sections from sporogonia of 

 various ages. 



ii. That the cells of this layer divide repeatedly ; and 

 ultimately, by division of each of the resulting spore- 

 mother cells into four, the spores are produced. 



Mount some mature spores in water : they will be 

 seen to be of spherical form, with smooth walls, and 

 granular, oily contents. 



XIV. In order better to understand the structure and 

 origin of the peristome, cut off transversely the whole 

 orange-coloured tip of a sporogonium of Funaria, and 

 mount it with the apex uppermost in weak glycerine : 

 observe under a low power 



i. The contorted brown teeth of the peristome, 

 sixteen in number : these are easily seen through 



ii. The more transparent operculum, which covers 

 them : by focusing carefully downwards 



iii. The much thickened cells of the annulus may 

 also be distinctly seen. 



XV. Cut thin transverse sections of the operculum 

 of a still unripe sporogonium : in those which pass imme- 

 diately above the annulus, observe at the periphery 



a. The thickened epidermis, and beneath it two or 

 three layers of thin-walled cells : these together with the 

 epidermis constitute the operculum : then follows 



