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efficiently in catching" and holding the sand during the summer. 

 After the death of the leaves and culms in the autumn, they still 

 persist, and continue to build up the dune during the winter. These 

 dead bunches are frecjuently partly covered, but the new growth of 

 the succeeding spring comes up through the sand, and bunches en- 

 tirely destroyed by burial were not observed. The species is accord- 

 ingly a vei*y efficient dune-former, and builds up steep dunes from 

 two to ten feet (1-3 m.) high. The infrequency of the plant in 

 situations from which sand is being removed gives no opportunity 

 to estimate its ability to withstand uncovering. In a few cases relic 

 bunches have been seen on windward slopes, but it is probably not 

 well adapted to undermining. 



RJius canadensis, van iUinociisis, while not so abundant as Pani- 

 cmn mrgatuni, is the most effective dune-former in our inland dunes. 

 It is characteristically a species of the open bunch-grass association 

 (PI. VII, Fig. i), where it produces dense rounded thickets up to a 

 yard (i m.) in height and frequently several yards across. These 

 thickets are so dense that at a little distance they appear' as a solid 

 mass of foliage. Within there is a tangle of stems, with the leaves 

 mostly near the ends. The roots are long, and penetrate very deeply 

 into the soil. Fniit is produced abundantly and is probably scattered 

 widely by birds, yet comparatively few young" plants are seen 

 and none at all have been seen on the deposits of the blowouts. 

 Its presence there is probably in most cases due to persistence from 

 the bunch-grass which preceded the blowout. It may occur, there- 

 fore, at either side or at the deposit end. The number of blowouts 

 where it so occurs depends upon its fre([uency in the adjoining , 

 bunch-grass. It has not been observed in the Panicuin pscudopu- 

 hescens association or on the windward slopes of the l)lowouts. The 

 efficiency of the plant in building up dunes is due to its habit of 

 g'rowth in dense compact masses and to its ability to withstand burial 

 by sand. The blowing sand is caught and held by the dense thickets, 

 and accumulates in a rounded heap conforming to the shape of the 

 thicket. The accumulation continues until the sand reaches within 

 six or eight inches (1-2 dm.) of the top of the thicket. There is 

 little dift'erence in the outward appearance of such a partly buried 

 thicket, although the leafy twigs protrude l)ut a few inches above the 

 sand. When the leaves fall in autumn they also tend to accumulate 

 between the twigs and thus protect the sand from erosion during the 

 winter. The sumach is not injured by this partial burial, but in each 

 successive season grows farther upward and outward, maintaining 

 its position above the sand and causing" the rapid growth of the dune. 



