The interfascicular cambium develops from the cells of -

In heartwood,the conduction of sap is mostly blocked due to the presence of:

Identify the correct statements:
$A$. Lenticels are the lens-shaped openings permitting the exchange of gases.
$B$. Bark formed early in the season is called hard bark.
$C$. Bark is a technical term that refers to all tissues exterior to vascular cambium.
$D$. Bark refers to periderm and secondary phloem.
$E$. Phellogen is single-layered in thickness.
Choose the correct answer from the options given below:

In a stratified cambium,the fusiform initials are

Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.

Select the wrong statement regarding secondary phloem.