112 PHARMACEUTICAL BOTANY 
SECONDARY TissuEs are those which take their origin in a 
cambium or cork cambium. Examples of secondary tissues 
Oo 
is 
Eo 
Sel ry 
+3 ws 
a ns 
1s 
Poel © é 
idermi ay TARY 
ast fiber RR TS Zee % 
Y SRT (Va 
ollenchyma 
ACCC rrittrrrr 
CHSC A 
tS HTD 
\Rtates wstareatene 
3° 
OTA ° 
LY sen: I) ‘4 
DAT es 
Y 
+ 
ee 
( 
BA) 
ere! 
ay 
ahs 
on 
anes 
ry 
nee 
BY) 
= 
ae 
bi 
CRS 
Yad s 
LV 
ears 
BS: 
4 
os 
V eo X 
ylem from the Procambium 4 Xylem from the procambiumn 
Xylem.from the cambium Xylemfrom the cambium 
Phloem from the procambium and cambium Phloem from the procambium and cambium 
Fic. 56.—Diagram showing the evolution of tissues in a stem from the pri- 
mordial meristem down to the beginning of cambial activity. In the longitudinal 
diagram, at the bottom, the initial C of the word cambium stands directly beneath 
this tissue which is radially but one cell in thickness. (After Stevens.) 
oe 
are secondary xylem and secondary phioem which arise from a primary 
cambium, and cork and secondary cortex which arise from cork 
cambium. ‘These will be discussed more fully in a later part of 
this chapter. 
