ASPIDIUM SPOROPHYTE 307 



1. The form of the apical cell, apparently three- 

 sided : combining this result with that obtained by 

 examination of the longitudinal sections the form of 

 the whole cell must be a three-sided pyramid. 

 (Compare Fig. 13.) 



2. The segments are arranged in regular order 

 round it, and are cut off successively from the three 

 sides. 



3. Note the mode in which the several segments are 

 further divided. 



Next examine a section which has passed through 

 the root-cap immediately above the apical cell : 

 this will include the young segments cut off from the 

 base of the apical cell by transverse walls, and destined 

 to form the root-cap. Note the first divisions of these 

 segments by walls arranged crosswise : it may be seen 

 that these walls do not coincide in position in successive 

 segments. 



The Leaf. 



XVI. Cut transverse sections of a pinna of a leaf of the 

 Male Fern which has no sori upon it : mount in weak 

 glycerine, and observe with a low power that the out- 

 line of the section shows the leaf to be of equal thick- 

 ness throughout, except where traversed by vascular 

 bundles : at those points the pinna is thickened, the 

 lower surface projecting convexly. 



Examine with a high power, and observe succes- 

 sively the following tissues, starting from the upper 

 surface : 



1. A regular epidermis with a thin cuticle: the 



x 2 



