While observing a section many scattered vascular bundles could be seen. Teacher said but in spite of this large number the stem cannot grow in girth. Why?

The transverse section of a plant shows following anatomical features :(i) Large number of scattered vascular bundles surrounded by bundle sheath. (ii) Large conspicuous parenchymatous ground tissue. (iii)Vascular bundles conjoint and closed.

Student while observing a slide of leaf section observed many stomata on the upper surface. He thought he has placed slide upside down. Teacher confirmed it is rightly placed. Explain.

A student was observing a slide with no label under microscope. The section had some vascular bundles scattered in the ground tissue. It is section of a monocot stem! He exclaimed. No! It is section of fern rachis, said the teacher. Teacher told to observe vascular bundle again. Student agreed. Why?