PLATE XXXVIII
FRAGILE BLADDER FERN
a Portion of fertile pinna
b Tip of fertile pinna
c Magnified fruit-dot showing indusium
53. FRAGILE BLADDER FERN. COMMON BLADDER FERN
Cystopteris fragilis
A rock and wood fern, found from Newfoundland to Georgia. Six to eighteen inches long, with slender and brittle stalks, green except at the base.
Fronds.—Oblong-lanceolate, thin, twice to thrice-pinnate or pinnatifid; pinnæ lance-ovate, irregularly cut into toothed segments which at their base run along the midrib by a narrow margin; fruit-dots roundish, often abundant; indusium early withering and exposing the sporangia, which finally appear naked.
This plant may be ranked among the earliest ferns of the year. In May or June, if we climb down to the brook where the columbine flings out her brilliant, nodding blossoms, we find the delicate little fronds, just uncurled, clinging to the steep, moist rocks, or perhaps beyond, in the deeper woods, they nestle among the spreading roots of some great forest tree. Their "fragile greenness" is very winning. As the plant matures, attaining at times a height of nearly two feet, it loses something of this first delicate charm. By the end of July its fruit has ripened, its spores are discharged, and the plant disappears. Frequently, if not always, a new crop springs up in August. We are enchanted to discover tender young fronds making patches of fresh green in every crevice of the rocks among which the stream forces its precipitous way. Once more the woods are flavored with the essence of spring. In our delight in this new promise we forget for a moment to mourn the vanishing summer.
The outline of the Common Bladder Fern suggests that of the Obtuse Woodsia. The two plants might be difficult to distinguish were it not for the difference in their indusia. At maturity the indusium of the Common Bladder Fern usually disappears, leaving the fruit-dot naked, while that of the Obtuse Woodsia is fastened underneath the fruit-dot and splits apart into jagged, spreading lobes.
The sterile fronds of the Slender Cliff Brake also have been thought to resemble this fern, in whose company it often grows.
Williamson says that the Common Bladder Fern is easily cultivated either in mounds or on rock-work.