354 PKACTICAL BOTANY 



orange- coloured tip of an unripe 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. 



b. Beneath this is found a layer of cells with peculiar 

 thickening bands on the inner and outer walls : these 

 bands separate, by rupture of the thinner parts of the 

 walls, as the inner and outer peristome, which thus 

 consists when mature of ribbands of cell-wall, and not 

 of complete cells. 



The above points may with advantage be confirmed 

 by observations on mature sporogonia. 



For comparison with the sections above described, transverse 

 and longitudinal sections may be cut from young sporogonia of 

 Funaria of various ages, and the development of this peculiar 

 organ may thus be traced. For details of description see the 

 text-books ; especially Goebel's Outlines, Eng. Ed., p. 186. 



XVI. Longitudinal and transverse sections may 

 also be made from the sporogonium of PolytricJium 

 commune, which may be treated as above directed. 

 The chief differences from Funaria will be as follows- 



