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PRACTICAL BOTANY 



immediately surrounding it are arranged in more regular 

 order than those at a greater distance. This cell is the 

 apical cell, and the cells surrounding it have been 

 derived by cell-division from it, by means of walls 

 parallel to its three sides : they are called the seg- 

 mental cells, and it may readily be seen that these 

 again undergo subdivision. If the section be not 

 sufficiently transparent, it may be treated with very 

 dilute potash and weak glycerine, or, better, with " eau de 

 javelle," which will clarify the tissues, and make the 

 cell-walls more distinct. 



The form of the apical cell, and of the segmental 

 cells which surround it, will be readily appreciated on 

 comparison of Fig. 13. 



FIG. 14. Diagram showing the arrangement of cell-walls as seen in a median longi- 

 tudinal section through an apical cone with a pyramidal apical cell. A A, are the 

 segmental walls, which form part of the system of anticlinals ; a, a, walls by 

 which each segment is cut into two equal halves : these complete the anticlinal 

 curves ; P P, periclinals, which are not completed up to the apex. (After Sachs. ) 



XII. From the apex of another plant cut median 

 longitudinal sections : mount in weak glycerine : a 



