216 



XVI. THE STEM APEX. 



Javelle, or else by the use of a little potash. Should this latter 

 act too strongly, and have " cleared" the growing apex, until its 

 cell-walls become unrecognisable, we can remedy the evil by a 

 suitable addition of water. In fresh sections we must avoid the 

 use of any water-withdrawing medium, as otherwise the growing 

 apex will collapse. Sections of alcohol material can, on the other 

 hand, be laid in glycerine direct, but not after they have been 

 previously placed in water. Sections treated with Eau de Javelle 

 cannot be placed at once into concentrated glycerine, but must be 



FIG. 85. Longitudinal section through the growing apex of a main vegetative shoot 

 of Equisetum a-rvense ; t, apical cell ; ?, youngest, 8", next older segment ; p, primary 

 wall ; i, segmenting wall ; pr, later periclinal ; a, later anticlinal walls ; f, first ; ,/*', 

 second,/", third whorls of leaves ; g, initial cell of an axillary bud (x 240). 



placed in very dilute glycerine, which is allowed to concentrate by 

 standing in the air. Sections made transparent with potash can 

 be neutralised with acetic acid, and preserved in acetate of potash. 

 As it is of special importance to be able in this case to view the 

 section alternately from its two sides, we lay it, as we did in the 

 case of Hippuris, between two cover-glasses. 



If the growing apex is cut in the proper direction, it presents 

 its apical cell (a three -sided pyramid upon a convex base), in the 

 form of an obtuse wedge, the apex of which is sunk in the tissue 

 of the growing point, and its base is arched free towards the 



