154 Journal of the Mitchell Society [March 



macrorhiza. And quite i-ecently (Ma}-, 1921) the writer has traversed 

 over 100 miles of the river above Tuscaloosa in a canoe, with frequent 

 landings, without materially extending the known distribution of any 

 of the plants mentioned below, not even those which have their 

 southernmost outposts near the fall line. 



Before listing the rare plants some additional features of the en- 

 vironment may be mentioned. At the point where they are most num- 

 erous and for a few miles farther upstream, the hilltops are capped 

 with sand and pebbles of Cretaceous or later age, belonging to the 

 coastal plain, and characterized by forests of Pinvs pahistris and its 

 common associates, subject to frequent fires, as is usual throughout 

 the range of that tree. In the same neighborhood the lowlands on the 

 inner sides of bends are covered with ''second bottom" or terrace de- 

 posits, which extend all the way to the coast but are very slightly 

 represented upstream; and ^Acer saccharinum (formerly A. dasycar- 

 puni), which is perhaps more nearly confined to river-banks than any 

 other tree in the eastern United States, and seems to require twenty 

 feet or more of seasonal fluctuation of water, extends up the river 

 just about to the point under consideration. Quercus laurifolia, which 

 is almost confined to the coastal plain, extends a few miles farther 

 upstream. 



But all this perhaps has as little to do with the peculiarities of 

 the cliff flora as the fact that some of the river water comes from a 

 limestone valley. It may be a little more significant that there are 

 among these cliffs several ' ' hanging valle.ys, ' ' with mouths high above 

 the river, presumably indicating that the streams which made them 

 are dry most of the time, and therefore have not cut down their chan- 

 nels as fast as the river has. Springs too are scarce along the river, 

 as the canoeist discovers to his discomfort in hot weather. This indi- 

 cates that there must be little leaching out of the elements of fertility 

 from the rocks. 



Some of the plants under consideration are of species commonly 

 supposed to be partial to limestone, although the rock is not notice- 

 ably calcareous. A partial analysis of a specimen of the shale made 

 for the writer some years ago showed only 0.42% of lime (CaO), but 

 nearly ten times as much potash (K^,0), namely, 3.95%^; and it is 

 quite likely that these and many other supposed calciphiles are really 



See Geol. Surv. Ala. Monog. 8: 54. 1913. 



