Option 1: Sciophilous refers to plants that thrive in shaded and dark areas. These plants are adapted to low light conditions.

Option 2: Xerophytes are plants that can tolerate and adapt to dry and arid environments. Their growth is not specifically dependent on light, but on their ability to conserve water.

Option 3: Heliophytes are plants that require and prefer ample sunlight for their growth. These plants have adapted to thrive in areas with high light levels.

Option 4: Epiphytes are plants that grow on other plants but do not rely on them for nourishment. Their growth can vary in light requirements, but it is not solely limited to light.

Therefore, the correct answer is option 3, as the plants that grow well only in light are known as heliophytes.