



60 : FLOWERING PLANTS 
sity for a layer of meristematic cells once the bundles are 

. 
oa 
<) 
1G 
cS 
iD 
OS 
A@ 
ee 
»-*. 
ce 
ee 
DIG 
Coe. 
Fig. 28.—FIBRO-VASCULAR BUNDLE oF Mono- 
COTYLEDON, 
power. ) 
TRANSVERSE SECTION. 
(High 
p, pitted vessel; s, spiral ; a, annular; a.s, air 
space ;. s.¢, . sieve-tubes ; 
scl, sheath of fibres. 
w.f, wood- fibres ; 
formed, so that in 
M onocotyledons 
there 18 no cam- 
bium; the bundles 
are said to be 
closed; © As: in 
Dicotyledons, 
each bundle. con- 
sists of bast and 
wood. The wood 
is towards the 
centre, and the 
arrangement of 
the vessels 1s 
V-shaped. 
Formation Cork is 
of Cork. formed 
usually immedi- 
ately beneath the 
epidermis. As the 
stem grows in 
thickness, 
underlying tissues 
grow faster than the epidermis, which becomes torn, and 
therefore not a_ suffi- 
cient protection to the 
softer tissues under- 
neath, Even in herbs 
this is the case, and then 
cork cells are formed. 
Generally a layer of 
the cortical parenchyma 
immediately — beneath 
the epidermis begins to 
divide, and is then 
called cork  cambium 

ek 
sits 
OO) 
Slee 
zs OSS 
ck 



XX) 
5 


Fic. 29.—OpPEN LENTICEL, TRANSVERSE 
Section. (High power.) 
c.c, cork cambium ; ck, cork ; e, ruptured 
epidermis. 
> 
(Fig. 29, cc). This gives rise to layers of cells, which form 
the 

