- Pale persicaria, [120]
- Panicum, [113]
- Panicum capillare, [115]
- Panicum, smooth, [115]
- Papaveraceae, [132]
- Parsley family, [148]
- Parsnip, wild, [149]
- Pastinaca, [149]
- Patience dock, [123]
- Pennsylvania persicaria, [120]
- Penny cress, [137]
- Peppergrass, [135], [136]
- Persicaria, dock-leaved, [120]
- Pigeon grass, [117]
- Pigweed, [124]
- Pigweed family, [124]
- Pink family, [128]
- Plantago, [158], [159]
- Plantain family, [158]
- Poa annua, [116]
- Poa compressa, [116]
- Poa, flat-stemmed, [116]
- Poa pratensis, [116]
- Poison hemlock, [148]
- Poison ivy, [145]
- Polygonaceae, [119]
- Polygonum, [119]-120
- Poppy family, [132]
- Porcupine grass, [117]
- Portulaca, [131]
- Portulacaceae, [131]
- Potentilla, [138], [139]
- Prickly lettuce, [168]
- Prickly sida, [146]
- Prostrate amaranth, [127]
- Prunella, [155]
Pu-bes´cent, clothed with soft and rather short hairs.
- Pulse family, [139]
- Purple Jimsonweed, [155]
- Purple-stemmed beggar-ticks, [163]
- Purslane family, [131]
- Purslane speedwell, [157]
- Pusley, [131]
- Quack grass, [110]
Ra´phe, the adherent funiculus connecting the hilum and chalaza in anatropous or amphitropous ovules or seeds.
Re-tic´u-late, in the form of network.
Root, the descending axis which is destitute of leaves or nodes.
Root stock, rhizome, a stem usually subterranean and more or less thickened, producing young branches.