(318)__Selaginella selaginoides, commonly known as low spike-moss;

(319)__Sericocarpus asteroides, commonly known as white-topped aster;

(320)__Shepherdia canadensis, commonly known as Canada buffaloberry;

(321)__Silene acaulis, commonly known as moss campion;

(322)__Sisyrinchium mucronatum, commonly known as Michaux's blue-eyed-grass;

(323)__Solidago altissima, commonly known as tall goldenrod;

(324)__Solidago x calcicola, commonly known as rock goldenrod;

(325)__Solidago multiradiata, commonly known as Cutler's goldenrod;

(326)__Solidago ulmifolia, commonly known as elm- leaved goldenrod;

(327)__Sorghastrum nutans, commonly known as Indian grass;

(328)__Sphenopholis obtusata, commonly known as prairie wedge-grass;

(329)__Spiraea septentrionalis, commonly known as northern meadow-sweet;

(330)__Spiranthes lacera var. gracilis, commonly known as southern slender ladies' tresses;

(331)__Spiranthes lucida, commonly known as shining ladies'-tresses;

(332)__Sporobolus asper, commonly known as longleaf dropseed;

(333)__Sporobolus neglectus, commonly known as small dropseed;