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 Sneeze Weed, 128 Sneezewort, 131 Snowberry, 85, 111 Soapberry Family, 70 Soapwort, 34 Solanaceae, 100 Solanum, 100 Solidago, 125-127 Solomon's Seal, 11 Sorbaria, 57 Sorrel, Red, 25 Sorrel, Green, 25 Sorrel, Wood, 64 Sour Dock, 26 Sour Gum, 83 Southernwood, 119 Sparganiaceae, 2 Spartina, 5 Spear Grass, 7 Spearmint, 98 Spearwort, 36 Speckled Alder, 22 Specularia, 112 Speedwell, 105 Spergula, 32 Spergularia, 32 Spice Bush, 41 Spiderwort, 9 Spiderwort Family, 9 Spikenard, 80 Spike Rush, 7 Spiraea, 53 Spiranthes, 16 Spirodela, 9 Spotted Wintergreen, 85 Spurge, 67, 68 Spurge Family, 66 Spurred Gentian, 89 Spurrey, 32 Spring Avens, 56 Spring Beauty, 34 Spring Vetch, 59 Spruce, 1 Squashberry, 111 Squaw-root, 106 Squaw Weed, 128 Squirrel Corn, 41 Squirrel-tail, 4 Stachys, 99 Staff Tree Family, 69 Staphylea, 69 Staphyleaceae, 69 Star Flower, 87 Star Grass, 14 Star of Bethlehem, 14 Starry Campion, 33 Steironema, 88 Stellaria, 32, 33 Stemless Lady's Slipper, 18 Stickseed, 94 Stinging Nettle, 24 Stitchwort, 32 St. John's-wort, 73, 74 St. John's-wort Family, 73 Stone Clover, 61 Stonecrop, 48 Stonecrop, Ditch, 49 Stork's-bill, 64 Strawberry, 56 Strawberry, Barren, 55 Strawberry Blite, 29 Streptopus, 11 Striped Maple, 70 Strophostyles, 58 Stylophorum, 41 Sugar Maple, 70 Sumach, 68, 69 Summer Grape, 72 Summer Savory, 97 Sundew, 48 Sundew Family, 48 Sundrops, 78 Sunflower, 128-130 Sunflower, Tickseed, 124 Swamp Birch, 22 Swamp Currant, 49 Swamp Dewberry, 53 Swamp Laurel, 85 Swamp Milkweed, 91 Swamp Rose, 52 Swamp Valerian, 111 Swamp White Oak, 23 Sweet Birch, 22 Sweetbrier, 52 Sweet Cicely, 82 Sweet Fern, 20 Sweet Flag, 8 Sweet Gale, 21 Sweet Gale Family, 20 Sweet White Violet, 76 Sweet William, 34, 92 Sweet William Catchfly, 34 Sycamore, 51 Symphoricarpos, 110, 111 Symphytum, 93 Symplocarpus, 8 Synthyris, 102 Syringa, 88 Taenidia, 81 Tall Dock, 26 Tamarack, 1 Tanacetum, 119 Tansy, 119 Tansy Mustard, 43 Taraxacum, 115 Taxaceae, 2 Taxus, 2 Tear-thumb, 28 Teasel, 112 Teasel Family, 112 Tephrosia, 60 Teucrium, 97 Thalictrum, 39 Thaspium, 81 Thistle, 117, 118 Thistle, Canada, 118 Thistle, Cotton, 118 Thistle, Globe, 117 Thistle, Milk, 117 Thistle, Russian, 28 Thistle, Sow, 117 Thlaspi, 46 Thorn-apple, 100 Thorny Amaranth, 30 Three-seeded Mercury, 66 Three-square, 7 Thuja, 1 Thymelaeaceae, 77 Thyme, Wild, 97 Thymus, 97 Tiarella, 51 Tickseed, 123, 124