erican varieties not air-plants;
form of flower, 181;
elasticity of the pollen of the _Spectabilis_, 182;
self-fertilizing, 183;
American and exotic species, 184;
Arethusa's fragrance, 185;
its structure, 186;
significant depth of nectar wells;
conditions demanded of insects, 187;
Gray's surmise, 188;
sphinx-moth its only complement, 190;
manner of carrying the pollen by sphinx-moth, 193;
extracting the pollen with a pencil;
length of the nectary, 196;
purple-fringed, 198;
ragged, 200;
very exceptional provision, 201;
yellow-spiked, 203;
moccasin-flower;
ladies'-slipper;
Venus's-slipper;
the color of, 205;
distinctive character of, 206;
practical experiment, 209;
imprisonment of the bee;
manner of its release, 210;
rattlesnake-plantain, 213;
Angraecum, its long nectary, 219;
tongue of a sphinx-moth eleven inches long, 220;
nectary thirteen inches long, 223.

"Origin of Species":
--First important presentation of the theory of
cross-fertilization, 105;
tardy appreciation of the work, 115.

_Odynerus flavipes_, wren-wasp, 10.

Ovid, concerning hornets, 18.

Parallels in Nature, 152.

Platanthera, orchid group, 192.

Pliny, 23.

_Pogonia ophioglossoides_, sweet-pogonia, 145.

Polistes, brown wasp, 161.

Primrose, evening, 118.

Psychid:
--A sack-bearer; drags its house with it; feeds on seed-pods, 83;
winter quarters of silk, 84.

Queer Little Family:
--Tree-hopper (_Membracis binotata_); a singular entertainment;
graceful curves, 87;
a branch in masquerade; queer thorns, 88;
a sudden disappearance; animated thorns; like a covey of quails, 89;
like "Bob White," 90;
singular agility; queer anatomy; always ready for flight, 91;
fondness for locust and oak-trees, simulating the color and character
of the branches, 92;
manner of sitting on the branches, 93;
always headed towards the top; tiny tufts of cotton, 94;
color and size of the tufts; a mere frothy shell; a riddle, 95;
its relations, 96;
an investigation, 97;
its technique, 98;
aerated cement; froth-house builder, 99;
period of hatching, 100;
a house for the winter; not a wanderer, 101.

Ragged Orchid (_H. lacera_), 200.

"Rattlesnake-plantain," 213.

_Rudbeckia hirta_, cone-flower, 138.