PHARMACEUTICAL BOTANY 



Histology of Growing Apex. When the bases of the leaves of the 

 current year, the circinate leaves of the following year and the large 

 mass of brown scales have been removed from around the apical bud 

 of a well-grown plant, tjie following structures may readily be ob- 

 served with a hand lens : 



1. The apical cone (punctum vegetationis 4 ) , a rounded papilla, which 

 occupies a terminal position in the apical region. 



2. The young fronds, arranged around the apical cone. 



Upon removing the extreme apex of the apical cone with a sharp 

 razor, mounting in dilute glycerine or water and examining under 



low power, it will be noted 

 that a large pyramidal cell 

 occupies the center of the 

 apical cone. This is the 

 apical cell (Fig. 14). The 

 cells surrounding it have 

 been derived by segmenta- 

 tion (cell-division) from it, 

 by means of walls parallel 

 to its three sides; they are 

 termed segment cells and in 

 turn undergo further di- 

 vision and redivision to . 

 originate the entire stem 

 tissue and leaf tissue. Step 

 by step the tissue cells become modified into epidermal, cortical, 

 bundle and fundamental cells. 



Histology pf Mature Root. Transverse sections cut some dis- 

 tance above the apex will present the following structures for 

 examination : 



1. Epidermis, of epidermal cells whose outer walls are brown. 

 Some of these cells have grown out as root hairs which surround soil 

 particles and absorb water with mineral salts in solution. 



2. Cortex, of many layers of cortical parenchyma cells with brown 

 walls. The outer layers of cells of this region are thin-walled, while 

 the extreme inner ones are lignified and form a sclerenchymatous 

 ring which surrounds the 



FIG. 14. Apical cell of a fern rhizome in 

 vertical longitudinal section. a.c., apical 

 cell; h, hair; m, meristem. (After Hofmeister.) 

 Sedgwick & Wilson's General Biology, 

 Henry Holt &" Co. 



