(i) It is a raised opening or pore on the epidermis of bark of stem and roots.
(ii) It is helpful in exchange of gases and transpiration.

(a) Bark protects the plant from parasitic fungi and insects.
(b) It prevents water loss by evaporation and guards against variations of external temperature.
(c) It is an insect repellent, and is decay proof, fire proof.
(d) It is also a source of drugs and spices.

Phellem (cork) like cells which lack suberin in their walls.

In the spring season, because cambium is very active and produces a large number of xylary elements having vessels / tracheids with wide lumen.

(i) If the bark of a tree is damaged by the horn of a deer, the tree first seals the damaged region from microbial infection.
(ii) This happens by altering the chemistry of the affected area by forming a callus, which grows and covers the damaged area.

Annual Rings
(i) The activity of Vascular cambium is under the control of many physiological and environmental factors.
(ii) In temperate regions, the climatic conditions are not uniform throughout the year.
(iiii) In the spring season, cambium is very active and produces a large number of xylary elements having Vessels/tracheids with wide lumen.
(iv) The wood formed during this season is called spring wood or early wood.
(v) The tracheary elements are fairly thin walled.
(vi) In winter, the cambium is less active and forms fewer xylary elements that have narrow vessels tracheids and this wood is called autumn wood or late wood.
(vii) The tracheary elements are with narrow lumen, very thick walled.
(viii) Spring wood is lighter in colour with lower density.
(ix) Autumn wood is darker and has higher density.
(x) Sometimes Annual rings are called growth rings but all growth rings are not annual rings.
(xi) In some trees more than one growth ring is formed within a year due to climatic change.
(xii) Additional growth rings are developed within a year due to adverse natural calamities like drought, frost, defoliation, flood, mechanical injury and biotic factors during the middle of a growing season, which results in the formation of more than one annual ring. Such rings are called pseudo or false-annual rings.
(xiii) Each annual ring corresponds to one year's growth and on the basis of these rings, the age of a particular plant can easily be calculated.
(xiv) The determination of the age of a tree by counting the annual rings is called dendrochronology.

(i) Lateral meristem increases the girth in both stem and root
(ii) Secondary growth in dicots and gymnosperms is brought about by two lateral meristems
(iii) Vascular cambium
(iv) Cork Cambium
(v) Vascular cambium produces the secondary vascular tissues. i.e. Secondary xylem and Secondary phloem.

It is a gum got from the incisions on the bark of Acacia senegal. It exudes as a viscous liquid, collects in a drop and hardens.

(i) In gymnosperms, the resin ducts are blocked by tylose like ingrowths from the neighbouring resin producing parenchyamatous cells. Eg: Pinus.
(ii) In angiosperms, the sieve tubes are blocked by tylose- like ingrowths from the neighbouring parenchyamatous cells. Eg: Bombax. These are called tylosoids

(i) If the phellogen forms a complete cylinder around the stem, it gives rise to ring barks. Eg: Quercus.
(ii) When the bark is formed in overlapping scale like layers, it is known as scale bark. Eg Guava.
(iii) While ring barks normally do not peel off, scale barks peel off.

(i) In many dicot plants, the lumen of the xylem vessels is blocked by many balloonlike ingrowths from the neighbouring parenchymatous cells. These balloon-like structures are called tyloses.
(ii) Usually, these structures are formed in secondary xylem vessels that have lost their function i.e., in heart wood. In fully developed tyloses, starchy crystals, resins, gums, oils, tannins or coloured substances are found.

(i) The log A will last longer for the merchant.
(ii) In any tree the outer part of the wood is pale in colour, is called Sap Wood, while the centre part is darker called Heart Wood.
(iii) Due to the presence of tyloses and their contents, the heartwood becomes coloured, dead and the hardest part of the wood.
(iv) The heartwood is more durable and more resistant to the attack of microorganisms and insects.