in, 223, 225; Fig. 121.

Plasmodium, 12.

_Plataneae_. See "Plane."

_Platanus_. See "Sycamore."

Plerome, 176.

Plum, 207.

_Plumbago_, _-ineae_, 212.

Pod, 156.

_Podophyllum_. See "May-apple."

_Podosphaera_, 66-70; Fig. 39.
general structure, 66.
structure of filaments, 68.
suckers, 68.
conidia, 68.
sexual organs, 68.
spore fruit, 68, 69.
spore sac, 69.

_Pogonia_, 166.

_Poinsettia_, 199.

Poison-dogwood, 198.

Poison-hemlock, 202.

Poison-ivy, 171, 198.

Poke-weed, 185; Fig. 97.

_Polemonium_, _-aceae_, 214; Fig. 118.

Pollinium, 165.

_Polycarpae_, 185.

_Polygala_, _-aceae_. See "Milkwort."

_Polygonatum_. See "Solomon's Seal."

_Polygonum_, _-aceae_, 184; Fig. 98.

_Polysiphonia_, 52; Fig. 29.

Pomegranate, 206.

Pond-scum, 22, 29, 30.

Pond-weed, 159; Fig. 86.

_Pontederia_. See "Pickerel-weed."

Poplar, 181, 183.

Poppy, 191.

_Portulaca_, _-aceae_. See "Purslane."

Potash (caustic), 4, 5, 59, 67, 75, 97, 106, 111, 151, 176, 179, 180.

Potassium, 2.

Potato, 215.

Potato-fungus. See "_Phytophthora_."

_Potentilla_. See "Cinquefoil."

_Potomogeton_. See "Pond-weed."

Prickly-ash, 198.

Prickly fungus. See "_Hydnum_."

Prickly-pear, 204.

Prickly-poppy. See "_Argemone_."

Primrose, 211.

_Primula_, _-aceae_. See "Primrose."

Prince's-pine, 210; Fig. 116.

Procarp, 51.

_Proteaceae_, 205.

Prothallium, 102, 103, 114, 122, 125, 133, 144, 177.

_Protococcus_, _-aceae_, 22, 74; Fig. 11.

Protophyte, 11.

Protoplasm, 7.
movements of, 7.

Pteridophyte, 102, 153.

_Puccinia_, 81; Fig. 47. See also "Wheat-rust."

Puccoon, 215.

Puff-ball. See "_Lycoperdon_."

Purslane, 185.

Putty-root. See "_Aplectrum_."

Pyrenoid, 25, 31.

_Pyrenomycetes_, 76.

_Pyrola_, _-aceae_, 210.

Quince, 170.

Quill-wort, 125, 126; Fig. 74.

Raceme, 174.

Radial fibro-vascular bundles, 138, 176.

Radish, 192.

_Ranunculus_, _-aceae_. See "Buttercup."

Raspberry, 207.

Ray-flower, 223.

Receptacle, 167, 207, 223.

Receptive spot, 106.

Red algae, 21, 49, 52, 53; Figs. 29-31.

Red-bud, 209; Fig. 115.

Red cedar, 79, 131, 141; Fig. 78.

Red-wood, 142.

Reference-books, 235-236.

_Reseda_, _-aceae_. See "Mignonette."

Resin, 130.

Resin-duct, 130, 135, 137.

Resting-spore, 28, 32, 37, 57.

Rheumatism-root. See "Twin-leaf."

_Rhexia_, 206.

_Rhizocarpeae_. See "Water-fern."

Rhizoid. See "Root-hair."