114 PHARMACEUTICAL BOTANY 
1. MERISTEM 8. Cork 
2. PARENCHYMA 9. LATICIFEROUS TISSUE 
3. COLLENCHYMA 10. SIEVE OR CRIBIFORM TISSUE 
4. SCLERENCHYMA 11. TRACHEARY TISSUE 
5. EprmpermIis 12. MEDULLARY RAYS 
6. ENDODERMIS 13. GLANDS AND SECRETION RESERVOIRS 
7. PERICYCLE 14. NECTARIES 
MERISTEM 
MERISTEM, frequently called embryonic tissue, is undifferenti- 
ated tissue composed of cells in the state of rapid division. The 
first kind of meristem to appear arises from the division of apical 
cells at or near the apices of roots, stems and leaves and is in 
these regions called PrimorpiAL MeristeM. The primordial 
meristem gives rise through cell divisions and slight differentia- 
tion to the Primary Meristems (flerome, periblem and dermatogen) 
which in turn develop the primary permanent tissues of plants. 
Primary meristems retain the power of independent growth and 
capacity for division as long as the plant part survives which 
contains them. Meristem is also found in other regions of 
plant organs such as the cambium and cork cambium, and is 
there called SeconpARY MeristeM. Secondary meristem is a 
derivative of primary meristem. It gives rise to the secondary 
permanent tissues. It loses with its transition to the permanent 
tissues the power of division and independent growth. 
CampiuM is a secondary meristem lying between the phloem 
and xylem in certain collateral bundles (intrafascicular cam- 
bium) or between the phloem and xylem portions of the medul- 
lary rays (interfascicular cambium). It is cylindrical and 
extends longitudinally through the plant body. The cambium 
is found in roots and stems of gymnosperms and dicotyledons 
where it divides to form secondary xylem and secondary phloem. 
These formations are responsible for the increase in diameter 
of these organs. (Cf. Fig. 76.) 
Cork CAMBIUM or phellogen originates in the pericycle of roots 
and in the epidermis or outermost layer of the cortex of stems. 
Through division of its cells it cuts off cork on its outer face and 
frequently secondary cortex on its inner face. (See Fig. 70.) 
