Topic summary
Microphylls
Extracted from the Wikipedia article Microphylls and megaphylls.
Leaf vasculature
The clubmosses and horsetails have microphylls, as in all extant species there is only a single vascular trace in each leaf. These leaves are narrow because the width of the blade is limited by the distance water can efficiently diffuse cell-to-cell from the central vascular strand to the margin of the leaf. Despite their name, microphylls are not always small: those of Isoëtes can reach 25 centimetres in length, and the extinct Lepidodendron bore microphylls up to 78 cm long.