i6o 



BOTANY. 



are connected with the upper end of the annulus on one side and 

 with the upper end of the stalk on the other side by thin-walled 

 cells, which may be termed connec- 

 tive cells, since they hold each lip cell 

 to its part of the opening sporangium. 

 The cells on the side of the sporangium 

 are also thin-walled. If we now ex- 

 amine a sporangium from the back, 

 or dorsal edge as we say, it will appear 

 as in the left-hand figure. Here we 

 can see how very prominent the annu- 

 lus is. It projects beyond the surface of 

 the other cells of the sporangium. The 

 spores are contained inside this case. 

 265. Opening of the sporangium and dispersion of the 

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



Fig 

 Under side 

 dium spinulosum showing 

 dots (sori). 



of pinna of Aspi- 

 fruit 



Fig- '35- 

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



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 a leaf on a piece 

 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 



