Which structure is not found in the leaves of a bean plant

In plants like Nymphaea which is attached emerged hydrophyte, the stomata are present on

While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called ?

Term 'meristem' was coined by

Cavity or a gland formed by the separation is

Which of the following is the function of heartwood?