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4,12<br />
4.14<br />
4.15<br />
4.12 TS of the lerminal bud of the dicotyledon Ligustnun<br />
vulgare (pri\'et). Normally privet is decussate bur in this<br />
bud a whorl of three leaves arises from the shoot apex (1).<br />
Kote how the primordIa of the youngest whorl of leaves (2)<br />
lie in the same relarh'e positions as the older ones (31<br />
arising from the axis (\\'0 nodes below. (LM x 70.)<br />
90<br />
I Shoot apex 3 Older leaves<br />
2 Youngest leaf primordia<br />
4.13<br />
4.13 Shoot tip of the succulent dicotyledon Aeonium,<br />
Note the closely-crowded leaves arranged in a spiral<br />
phyllotaxy (d., 4.11), (Copyright of T. Norman Tait.)<br />
4.14 RLS of Ihe apex of an axillary bud of the<br />
dicot}'ledon Phaseolus vulgaris (bean). The apex<br />
has a single tunica layer (I) and two leaf<br />
primordia (2) are visible while a leaf bumess (3) is<br />
also evident. Rib meristem (4) lies at the base of<br />
the apex, (G-Os. Phase: contrast LM x 450.)<br />
1 Tunica layer<br />
2 Leaf primordia<br />
3 Leaf buttress<br />
4 Rib meristem<br />
4.15 LS of the shoot apical regIon of the<br />
monocotyledon <strong>Zea</strong> <strong>mays</strong> (maize). Although at the<br />
shoot apex (1) the leaves form singly. with each<br />
new primordium (2) being initiated at 180· from<br />
the previous leaf (3), the leaf bases grow laterally<br />
and soon encircle the apex (d., I.23). Note the<br />
shallow sloping sub-apical margins bearing the<br />
leaves; here Ihe primary thickening merisrcm (4)<br />
divides mainly periclinally with the derintives<br />
differentiating into parenchyma uaverscd by the<br />
procamhial (5) slTands which supply the leaves<br />
(LM x 70,)<br />
1 Shool apex<br />
2 ew leaf<br />
3 Previous leaf<br />
4 Primary thlckemng mcristem<br />
5 Proc:ambial slrand
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