Though one hesitates to differ from Dr. Eaton, who described the fertile fronds as "nearly black in color" and said that they were "not very common," and that a young botanist might "search in vain for them for a long time," my own experience has been that the fresh ones are very evidently green and neither scarce nor specially inconspicuous.
I have found these fertile fronds apparently full-grown in June, though usually they are assigned to a much later date. They remain standing, brown and dry, long after they have sown their spores, side by side with the fresh fronds of the following summer.
Detail a in [Plate I] represents the so-called var. obtusilobata. This is a form midway between the fruiting and the non-fruiting fronds. It may be looked for in situations where the fern has suffered some injury or deprivation.
PLATE I
SENSITIVE FERN
a. Var. obtusilobata
2. OSTRICH FERN
Onoclea Struthiopteris
Nova Scotia to New Jersey, along streams and in moist woods. Growing in a crown, two to ten feet high.
Sterile fronds.—Broadly lance-shaped, once-pinnate; pinnæ divided into narrowly oblong segments which do not reach the midvein; stalk short, deeply channelled in front.