may be naked as in the polypody, but are usually covered with a thin,
delicate membrane, known as the indusium (Greek, a dress, or mantle). The
family or genus of a fern is often determined by the shape of its indusium;
e.g., the indusium of the woodsias is star-shaped; of the Dicksonias,
cup-shaped; of the aspleniums, linear; of the wood ferns, kidney-shaped,
etc.

[Illustration: Fig. 4]

In many ferns the sporangia are surrounded in whole or in part by a
vertical, elastic ring (annulus) reminding one of a small, brown worm
closely coiled (Fig. 4). As the spores mature, the ring contracts and
bursts with considerable force, scattering the spores. The spores of the
different genera mature at different times from May to September. A good
time to collect ferns is just before the fruiting season. (For times of
fruiting see individual descriptions or chronological chart on page 220.)

HELPFUL HINTS

The following hints may be helpful to the young collector:

1. A good lens with needles for dissecting is very helpful in examining the
sori, veins, glands, etc., as an accurate knowledge of any one of these
items may aid in identifying a given specimen. Bausch and Lomb make a
convenient two-bladed pocket glass for about two dollars.[1]

[Footnote 1: In the linen tester here figured (cost $1.50) the lens is
mounted in a brass frame which holds it in position, enabling the dissector
to use both hands. A tripod lens will also be found cheap and serviceable.]

[Illustration]

2. Do not exterminate or weaken a fern colony by taking more plants than it
can spare. In small colonies of rare ferns take a few and leave the rest to
grow. It is decidedly ill-bred to rob a locality of its precious plants.
Pick your fern leaf down close to the root-stock, including a portion of
that also, if it can be spared. Place your fronds between newspaper sheets
and lay "dryers" over them (blotting paper or other absorbent paper). Cover
with a board or slat frame, and lay on this a weight of several pounds,
leaving it for twenty-four hours; if the specimens are not then cured,
change the dryers. Mount the prepared specimens on white mounting sheets.
The regulation size is 16-1/2 by 11-1/2 inches. The labels are usually
3-3/4 by 1-3/4 inches. A sample will suggest the proper inscription.

HERBARIUM OF JOHN DOE
_Ophioglossum vulgatum_, L.
(Adder's Tongue)
Willoughby Lake, Vt.
August 19, 1911. Wet meadow.
Coll. X.Y.Z. Rather com