NOTEMBEB 29, 1912] 



SCIENCE 



761 



the water's edge on botli sides, where it is 

 visible from the railroad at least, it is bor- 

 dered by a thin fringe of small cypress trees 

 (Taxodium distichum). 



Observations on this tree in all the south- 

 eastern states and in fourteen different years 

 have led me to believe that it is rarely or 

 never found on the banks of rivers or other 

 bodies of water which have an average sea- 

 sonal fluctuation of more than ten or twelve 

 feet. Its trunk usually emerges from the 

 ground just about low-water mark, and its 

 enlarged base and " knees " are generally be- 

 lieved to reach up approximately to the aver- 

 age level of high water;* the figures just men- 

 tioned being about the maximum height re- 

 corded for these excrescences. ISTow the Miss- 

 issippi Eiver in the latitude of Lake Chicot 

 has a seasonal fluctuation of about forty feet, 

 and the cs^press is absent from its immediate 

 banks, though visible from the river in some 

 places where it grows in nearby sloughs not 

 directly connected with the main channel. 



Presumably, therefore, when the waters of 

 the Mississippi flowed through what is now 

 Lake Chicot the cypresses which fringe the lake 

 to-day did not exist. When the lake was cut 

 off from the river, in the manner described in 

 all treatises on potamology, its seasonal fluc- 

 tuations were of course at once greatly re- 

 duced, and conditions then became suitable 

 for the growth of the cypress on its banks. 

 Consequently if one could determine the age 

 of the oldest of these trees, by counting the 

 annual rings or otherwise, that would give a 

 minimum estimate of the age of the lake. As 

 I have seen this lake only from the train, I 

 have no data about the annual rings of its 

 cypresses, but there is some evidence of 

 another sort that they are comparatively 

 young for that species. 



Young cypress trees, of either species, are 

 spindle-shaped in outline, much like the typ- 

 ical conventional conifers of the cooler parts 

 of the northern hemisphere, while mature in- 

 dividuals are always more or less flat-topped, 

 a character by which they can often be dis- 

 tinguished from other trees at a distance of 



" See Bull. Torrey Bot. Club, 32 : p. 108, 1905. 



several miles.' At just what age Taxodium 

 distichum reaches its maximum height and 

 begins to develop a flat top has not been de- 

 termined, but very likely it is between 100 and 

 300 years.' The cypresses of Lake Chicot are 

 mainly spindle-shaped, and perhaps date back 

 only to the eighteenth century. 



This supposition could easily be tested by a 

 visit to the place in question with suitable 

 tools. At the same time the cypresses bor- 

 dering other ox-bow lakes along the Missis- 

 sippi, especially those lakes whose age is a 

 matter of historical record, should be ex- 

 amined from the same point of view. Addi- 

 tional evidence might be gathered from other 

 swamp trees, especially the tupelo gum, 

 Nyssa uniflora, which is common in sloughs 

 and rare or absent on river-banks, bearing 

 about the same relation to seasonal fluctua- 

 tions of water that Taxodium distichum does. 

 But the cypress is best for this purpose, on ac- 

 count of its longevity. 



EOLAND M. HaEPEE 



Universitt, Ala. 



on compaeestg ammonifying coefficients of 

 different soils 



In a recent publication' Professor W. G. 

 Sackett gives some interesting results of a 



''Hilgard ("Soils," 507-508, 1906), Cowles 

 ("Ecology," 734, 1911), and some other writers 

 have noted that the cypress when growing in up- 

 lands, such as parks, is spindle-shaped (see illus- 

 tration in Bep. Mo. Bot. Gard., 15: pi. 16, 1904), 

 and have tried to correlate shape with habitat. 

 C. S. Chapman (U. S. Bureau of Forestry, Bull. 

 56: 41-42, 1906) ascribes the flat top of cypress 

 in Berkeley County, South Carolina, to the dis- 

 ease known as "peckiness, " while Cowles, in the 

 work cited, considers the flat-topped trees dwarfed 

 on account of "the imperfect absorption which is 

 characteristic of swamps. ' ' But age alone would 

 seem to be a sufficient explanation of the differ- 

 ence in shape, since there is no doubt that all the 

 younger trees, whether in their native swamps or 

 in parks, are spindle-shaped, and the largest indi- 

 viduals known are flat-topped. 



' The species has been known to civilized man 

 only about 300 years, and presumably none of the 

 existing cultivated specimens are old enough yet 

 to have lost their juvenile form. 



