Final answer:
The microphylls of quillworts are awl-shaped at the base. They are a unique feature of the Isoetes genus, which includes aquatic plants with short internodes and rosettes composed of these awl-shaped leaves.
Step-by-step explanation:
The microphylls of quillworts are awl-shaped at the base and look like green porcupine quills, although they aren't rigid. Microphylls are the tiny leaves characteristic of certain plant groups like clubmosses, and they first evolved as microphylls in plant history. The genus Isoetes, known as the quillworts, features aquatic, unbranched plants with very short internodes. These plants form rosettes with awl-shaped leaves, which can be more than 10 cm in length. Quillworts, being part of the vascular plants, have developed structures that aid in photosynthesis and reproduction differently from mosses and liverworts, which have simpler structures and different reproductive strategies.