Rhamnus, 71

Rhexia, 77

Rhus, 68, 69

Ribes, 49, 50

River Weed, 48

River Weed Family, 48

Robinia, 58

Rock Cress, 46, 47

Rocket, Sea, 45

Rock-rose Family, 74

Rosa, 52

Rosaceae, 51

Rose, 52

Rose Family, 51

Rose Mallow, 72

Rose Pink, 89

Rosin Weed, 123

Round-leaved Orchis, 17

Round-leaved Violet, 75

Rowan Tree, 52

Rubiaceae, 108

Rubus, 53, 54

Rudbeckia, 128

Rue Anemone, 39

Rue Family, 65

Ruellia, 107

Rumex, 25, 26

Rush, 10

Rush Family, 10

Rush, Twig, 8

Russian Thistle, 28

Rutabaga, 43

Rutaceae, 65

Sabbatia, 89

Sagina, 32

Sagittaria, 3

Salicaceae, 19

Salix, 20

Salmonberry, 54

Salsify, 115

Salsola, 28

Sambucus, 109

Samolus, 87

Sandalwood Family, 24

Sand Bur, 5

Sand Cherry, 54

Sand Rocket, 42, 43

Sand Spurrey, 32

Sand Violet, 76

Sanguinaria, 41

Sanguisorba, 57

Sanicula, 82

Santalaceae, 24

Sapindaceae, 70

Saponaria, 34

Sarracenia, 48

Sarraceniaceae, 48

Sarsaparilla, 80

Sarsaparilla Family, 80

Sassafras, 41

Satureja, 97

Saururus, 19

Saxifraga, 50

Saxifragaceae, 49

Saxifrage, 50

Saxifrage Family, 49

Saxifrage, Golden, 50

Scarlet Oak, 23

Scheuchzeria, 3

Schneck's Oak, 23

Scirpus, 7

Scleranthus, 31

Scorpion Grass, 94

Scrophularia, 103

Scrophulariaceae, 101

Scrub Oak, 23

Scutellaria, 96

Sea Rocket, 45

Sea-side Crowfoot, 36

Sedge, 8

Sedge Family, 7

Sedum, 48, 49

Self-heal, 97

Seneca Snakeroot, 66

Senecio, 127, 128

Senna, Wild, 60

Setaria, 4

Shag-bark Hickory, 21

Sheep-berry, 111

Sheep Laurel, 85

Shepherdia, 77

Shepherd's Purse, 46

Shingle Oak, 22

Shin-leaf, 84, 85

Shooting Star, 87

Showy Lady's Slipper, 18

Showy Orchis, 17

Sicyos, 112

Sida, 72, 73

Silene, 33, 34

Silphium, 122, 123, 127

Silver Maple, 70

Silver Weed, 55

Silvery Cinquefoil, 66

Silybum, 117

Simarubaceae, 65

Sium, 81

Sisymbrium, 43-45, 47

Sisyrinchium, 15

Skullcap, 96

Skunk Cabbage, 8

Skunk Currant, 49

Slender Nettle, 24

Slippery Elm, 24

Slough Grass, 5

Small-flowered Crowfoot, 36

Small-fruited Hickory, 21

Small Snapdragon, 103

Small Solomon's Seal, 11

Smartweed, 27, 28

Smilacina, 14

Smilax, 11

Smooth Alder, 22

Snake Mouth, 18

Snakeroot, Black, 82

Snakeroot, Seneca, 66

Snakeroot, Virginia, 25

Snapdragon, 103

Sneezeweed, 127