The trunks rose tall and strong and slender, and the fronds were branches twenty or thirty feet long, with the many long, narrow green blades starting from the midrib at right angles in pairs.

The fronds are pale green, delicate and hairy beneath along the midrib and veins.

A frond is bipinnate (Latin, bis, twice) when the lobes of the pinnæ extend to the midvein as in the royal fern (Fig. 2).

The pinnæ of a frond are often pinnátifid when the frond itself is pinnate; and a frond may be pinnate in its lower part and become pinnátifid higher up as in the pinnátifid spleenwort just mentioned (Fig. 3).

Clintonianum (Gray Herbarium)] CRESTED MARGINAL FERN Aspídium cristàtum X marginàle Both the crested fern and Clinton's fern appear to hybridize with the marginal shield fern with the result that the upper part of the frond is like marginale and the lower like cristàtum, including the veining and texture.