206 PHARMACEUTICAL BOTANY 
arranged product of the spring growth abuts on the densely 
arranged product of the last summer and autumn growth and the 
sharp contrast marks the periods of growth. To the spring, 
summer and autumn regions of growth of each year is given the 
term of “Annuat Rinc.” By counting the number of these rings 
it is possible to estimate the age of the tree or branch. 
Primary Medullary Ray 
a ‘ A — Ay —— small : May. EXORD BS 
Bes, taker PT 7 . 5 ene 29: ; 
aCe. Op Moe 27 
> = aI LFS 
2 ; om 6S 
: eo 
~ EAA LAS 
ae Bi eosens 
ee re oer] 
Contian| —_ oe 
= SERN 
; = aes 
Spring | ¥ (55 0 nae aoe ee a 
Wood ita e Y cigee 
See 
ee 
Summer q e 
Wood 
Fic. 136.—Stem of Linden, showing detailed structure of a small square area 
of Fig. 135, magnified 200 times. S, sieve tubes; the dark spaces at one corner of 
the sieve-tubes are companion cells. V, pitted trachee. The summer wood 
consists of wood fibers interspersed with parenchyma. (From F. O. Bowers? ‘Plants 
and Man.” By permission of the Macmillan Co., Publishers.) 
Barx.—Bark is a term applied to all that portion of a woody 
exogenous plant axis outside of the cambium line. 
In pharmacognic work, bark is divided into three zones, 
these from without inward being: 
1. Outer Bark or Cork region (sometimes with epidermis). 
_ 2. Middle Bark or Cortex region. 
3. Inner Bark or Phloem region (sometimes with pericycle attached). 
