FERNS. 



255 



535. Opening of the sporangium and dispersion of the 

 spores. If we take some fresh fruiting leaves of the Christmas 

 fern, or of any one of many of the species of the true ferns just 

 at the ripening of the spores, and place a portion of it on apiece 

 of white paper in a dry room, in a very short time we shall see 

 that the paper is being dusted with minute brown objects which 

 fly out from the leaf. Now if we take a portion of the same 

 leaf and place it under the low power of the microscope, so that 

 the full rounded sporangia can be seen, in a short time we note 

 that the sporangium opens, the upper half curls backward as 



Fig. 290. 

 Four pinnae of adiantum, showing recurved margins which cover the sporangia. 



shown in fig. 294, and soon it snaps quickly, to near its former 

 position, and the spores are at the same time thrown for a consid- 

 erable distance. This movement can sometimes be seen with the 

 aid of a good hand lens. 



536. How does this opening and snapping of the sporan- 

 gium take place ? We are now more curious than ever to see 

 just how this opening and snapping of the sporangium takes place. 

 We should now mount some of the fresh sporangia in water and 

 cover with a cover glass for microscopic examination. A drop 

 of glycerine should be placed at one side of the cover glass on the 

 slip so that the edge of the glycerine will come in touch with the 

 water. Now as one looks through the microscope to watch the 



