FERN'S. 



161 



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 shown in fig. 138, and soon it snaps quickly, to near its 

 former position, and the spores are at the same time thrown for 

 a considerable distance. This movement can sometimes be 

 seen with the aid of a good hand lens. 



266. 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 

 how the 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 

 it one side of the cover 

 ^lass on the slip so that 

 the edge of the glycerine 

 will come in touch with 

 the water. Now as one 

 looks through the micro- 

 scope to watch the sporan- 

 gia, the water should be 

 drawn from under the cover 

 glass with the aid of some 

 bibulous paper, like filter Fig. 136. 



n ,„ pr nlnrpH <ir tVip prW Section through sorus of Polypodiuni vulgare 

 papei, piaceu tU uie CUgL showing different stages of sporangium, and one 

 Of the COVer glaSS On the >^MceHular capitate Eair. 



opposite side from the glycerine. As the glycerine takes the place 

 of the water around the sporangia it draws the water out of the 

 cells of the annulus, just as it took the water out of the cells of 

 the spirogyra as we learned some time ago. As the water is 



