Zea mays

4.24
4.24 TS of a vascular bundle from the stem of RDnun­
,ulus (buttercup). This herbaceous dicotyledon does not
undergo secondary thickening despite the presence of
fasdcular cambium (1) lying bc:twc:c:n the metaxylem (2)
and mc:m.phloc:m. The laner shows a distinctive panern of
large lumenc:d-sieve tubes (3) and smaller companion cc:lls
(4) reminiscent of many monocotyledons (d., 1.11). Axial
parenchyma (5), protoxylem (6), protophloem fibres (7).
(LM x 285.)
1 Fascicular cambium
2 Metaxylem
3 Sieve tubes
4 Companion cells
5 Axial parenchyma
6 Protoxylem
7 Prorophlaem fibres
4.26 T$ showing detail of the root cap of
the monoctyle:don Zea mays (maize). Note
the progressive increase in thickness of the
cell walls towards the margin of the cap.
Here the cells are breaking down and
sloughing their mucilaginous cell walls and
protoplasts to form mucigc:l (1) which is
secreted inlO the soil. (G-Os, LM x 5] 0.)
1 Mucigel
4.25 RlS of the: root tip of rhe monocotyledon Zea mays
(maize) showing a prominent cap covering the apex. The
cap OJ has its own distinct initials (calypuogen. 2) while
me epidermis and conex apparently arise from a common
tier of initials (3) adjacent to the calyptlogen. The
procambial central cylinder has itS own inaials (4). Note
the conspicuous files (5) of enlarged cells within the
procambium which represent rhe future metaxylem
c:lementS (cf., 4.8). (L\1 x 145.)
1 Root cap
2 Cap initials
3 Initials of epidermis
and cortex
4 Procambial initials
5 Potential meuxylem
93
4.26