=Sinus.= Interval between two lobes or divisions of a leaf; sometimes sharp-angular, sometimes rounded. =Spatulate.= Gradually narrowed downward from a rounded summit. =Spike.= A cluster of sessile or nearly sessile lateral flowers on an elongated axis. =Spray.= The smaller branches and ultimate branchlets of a tree taken as a whole. =Stamens.= The pollen-bearing organs of a flower, each stamen consisting of a filament (stem) and anther which contains the pollen. =Staminate.= Having stamens. =Sterile.= Variously applied: to flowers with stamens only; to stamens without anthers; to anthers without pollen; to ovaries not producing seed, etc. =Stigma.= Part of pistil which receives the pollen. =Stipels.= Appendages to a leaflet, analogous to the stipules of a leaf. =Stipules.= Appendages of a leaf, usually at the point of insertion. =Striate.= Streaked, or very finely ridged lengthwise. =Style.= Part of pistil uniting ovary with stigma; often wanting. =Sucker.= A shoot of subterranean origin. =Suture.= The line of union between parts which have grown together; most often used with reference to the line along which an ovary opens. =Terete.= Cylindrical. =Ternate.= In threes. =Tomentose.= Densely pubescent or woolly. =Truncate.= As if cut off at the end. =Umbel.= An inflorescence in which the flower stems spring from the same point like the rays of an umbrella. =Verticillate.= Arranged in a circle round an axis; whorled. =Villose= or =villous.= With long, soft hairs. =Whorl.= Arranged in a circle about an axis. INDEX. A Abele. (Populus alba, L.) 39, 40 Abies balsamea, Mill. _Fir balsam_ 20-22 =Abietacae.= (=Pinoideae=) 1-22 Larix 1-4 Pinus 4-12 Picea 12-18 Tsuga 19, 20 Abies 20-22 Acacia, (Robinia Pseudacacia, L.) 131, 132 (Robinia viscosa, Vent.) 132 Three-thorned. (Gleditsia triacanthos, L.) 129, 130