Addisonia 25 



(Plate 237) 



ALNUS RUGOSA 

 Smooth Alder 



Native of the eastern and middle United States 

 Family Betulaceae Birch Family 



Betula {Alnus) rugosa Du Roi, Harbk. Baumz. 1: 112. 1771. 

 Alnus serrulata Willd. Sp. PL 4: 336. 1805. 

 Alnus rugosa Spreng. Syst. 3: 848. 1826. 



The most common habitat of Alnus rugosa is along the borders 

 of ponds and streams and in swampy places, but it also grows, less 

 commonly, on hillsides. Its range includes most of the eastern and 

 middle United States, from Maine to Florida, and westward to 

 Minnesota and Texas; but its paleontologic record shows that it 

 formerly had a considerably wider geographic distribution. Leaves, 

 indistinguishable in their minutest details from those of the living 

 plants, have been found in the peat and lignitic debris of Quaternary 

 swamp deposits in Maryland, and similar, perfectly preserved 

 impressions of both leaves and pistillate aments were found in rocks 

 of Eocene Tertiary age in Oregon, British Columbia, and Alaska, 

 and were described and figured under the name Alnus serrulata 

 jossilis by Professor J. S. Newberry, in his "Later Extinct Floras of 

 North America," where he remarks that the fossil specimen "closely 

 resembles the leaves of A. serrulata, and I have been unable to find 

 any characters upon which to base a distinction." 



The specimen from which the accompanying illustration was 

 made was taken from a large shrub of native growth in the New 

 York Botanical Garden. 



The smooth alder is a deciduous, monoecious shrub, usually from 

 ten to twenty feet in height, but occasionally having the appearance 

 of a small tree and reaching a height of thirty or forty feet. The 

 bark, except on. the young snoots, which are more or less pubescent, 

 is smooth, brownish, and marked with lighter colored lenticels, 

 which often give to it a somewhat speckled appearance. The 

 leaves are obovate or oval, rounded and obtuse at the summit, 

 wedge-shaped or occasionally rounded at the base, finely denticulate 

 on the margin, green on both sides, but somewhat darker above 

 than below, smooth except on the veins, which, especially on the 

 under surface, are clothed with a fine white or rufous pubescence. 

 The flower-buds, consisting of separately clustered staminate and 

 pistillate aments, or catkins as they are more commonly known, 

 are formed late in summer, remain dormant during the following 



