i8o A NATURALIST IN THE GREAT LAKES REGION 



saxifrage. The buttonbush, or elbow bush (Fig. 196), is a low 

 shrub with abruptly bent branches, which give it the name elbow 

 bush. It bears large, egg-shaped leaves, rather pointed at both 

 ends. The flowers which are small and white occur in spherical 

 clusters. The marsh marigold or cowslip is familiar to almost 

 everyone. Swamp saxifrage (Fig. 197) has long, slender, lance- 

 shaped leaves that are mostly 

 basal; their borders are 

 toothed. The clustered flow- 

 ers are yellowish green on long 

 slender stalks. Sensitive fern 

 is so unlike the other ferns 

 of the region that it may be 

 readily recognized from Fig. 

 198. The leaf is roughly 

 triangular and cut into large 

 lobes, not finely dissected as 

 are most of the fern leaves. 

 It is very sensitive to frost 

 and dies in the early fall. 



Still farther out on the 

 margin will be found a group 

 of plants that is common at 

 the outer edge of all the 

 marshes — sour gum, the 

 small-toothed trembhng pop- 

 lar, swamp holly, tw^o species 

 of Spiraea, the wdntergreen, the cinnamon fern, Clayton's fern, 

 and the royal fern. 



Sour gum (Fig. 199) is a deciduous tree that has, as a rule, a 

 trunk that runs straight to the top, as does the trunk of a pine. 

 The lower branches droop so that the tree has quite the appear- 

 ance of a conifer. The small-toothed trembling poplar has the 

 characteristic yellowish-green bark of the poplars. Its leaves 

 are small, finely toothed, and are borne on leafstalks that are 



Fig. 199. — Sour gum, Nyssa sylvatica 



