_Sieb. & Zucc._--Siebold, P. F. von, and J. G. Zuccarini. _Spreng._--Sprengel, Kurt. _Steph._--Stephani, F. _Steud._--Steudel, Ernst Gottlieb. _Sulliv._--Sullivant, William Starling. _Tayl._--Taylor, Thomas. _Thuill._--Thuillier, Jean Louis. _Thunb._--Thunberg, Carl Peter. _Thurb._--Thurber, George. _Torr._--Torrey, John. _Tourn._--Tournefort, Joseph Pitton de. _Tratt._--Trattenick, Leopold. _Tuckerm._--Tuckerman, Edward. _Turcz._--Turczaninow, Nicolaus. _Underw._--Underwood, Lucien M. _Vaill._--Vaillant, Sébastien. _Vent._--Ventenat, Étienne Pierre. _Vill._--Villars, Dominique. _Wahl._--Wahlenberg, George. _Wahlb._--Wahlberg, Pehr Fredrik. _Walp._--Walpers, Wilhelm Gerhard. _Walt._--Walter, Thomas. _Wang._--Wangenheim, F. A. J. von. _Web._--Weber, Friedrich. _Wigg._--Wiggers, F. H. _Willd._--Willdenow, Carl Ludwig. _Wils._--Wilson, William. _Wimm._--Wimmer, Friedrich. _With._--Withering, William. _Wormsk._--Wormskiold, M. von. _Wr. (Eat. & Wr.)_--Wright, John. _Wulf._--Wulfen, Franz Xaver. SIGNS USED IN THIS WORK. °, ´,´´ . The sign of degrees (°) is used for feet; of minutes (´), for inches; of seconds (´´), for lines,--the line being the twelfth part of an inch, and very nearly equivalent to two millimetres. µ. In microscopic measurements, the conventional sign for the micromillimetre or the one-thousandth part of a millimetre = one two-thousandth part of a line. ♂ Bearing only stamens or antheridia. ♀ Pistillate or bearing archegonia. ? A mark of doubt. ! A mark of affirmation or authentication. Figures or words separated by a short dash (--) indicate the extremes of variation, as "5--10´´ long, few--many-flowered," i.e. varying from 5 to 10 lines in length, and with from few to many flowers. BOTANY OF THE NORTHERN UNITED STATES. SERIES I. PHÆNOGAMOUS OR FLOWERING PLANTS. Vegetables bearing proper flowers, that is, having stamens and pistils, and producing seeds, which contain an embryo. CLASS I. DICOTYLEDONOUS OR EXOGENOUS PLANTS. Stems formed of bark, wood, and pith; the wood forming a layer between the other two, increasing, when the stem continues from year to year, by the annual addition of a new layer to the outside, next the bark. Leaves netted-veined. Embryo with a pair of opposite cotyledons, or rarely several in a whorl. Flowers having their parts usually in fives or fours. SUBCLASS I. ANGIOSPÉRMÆ. Pistil consisting of a closed ovary, which contains the ovules and forms the fruit. Cotyledons only two. DIVISION I. POLYPETALOUS EXOGENOUS PLANTS. Floral envelopes consisting of both calyx and corolla; the petals not united with each other. (Several genera or species belonging to Polypetalous Orders are destitute of petals, or have them more or less united.) ORDER 1. RANUNCULÀCEÆ. (CROWFOOT FAMILY.)