Mat 28, 1920] 



SCIENCE 



547 



can maintain life on low mineral rations; 

 (1) on account of its porosity it is always 

 well drained; (2) it is likewise well aerated; 

 (3) it allows free lateral and vertical move- 

 ment of ground water; (4) on account of its 

 low capillary absorption of water it has a 

 very low wilting limit ;^ in other words, it 



Water per 100 ol Dry Soil 



Wlien Plants Hygroscopic 



Wilt Water 



Ooaa-se eaud 1.5 1.15 



Sandy garden soil 4.6 3.00 



Fine sand, with humus. 6.2 3.98 



Sandy loam 7.8 5.74 



Chalky loam 9.8 5.20 



Peat 49.7 42.30 



gives up its water readily to plants and even 

 though it contains little, that little is avail- 

 able for the growth of vegetation; (5) it 

 offers little obstruction to the growth and ex- 

 tension of roots, when compared with stiffer 

 soils such as clay loams and clay. 



Probably its greatest physical disadvantage 

 is its tendency to drift with the wind with the 

 resultant root-uncovering or top-burying ac- 

 tion. However, this is not a serious menace 

 to typical dune vegetation for the great root 

 systems of most dime plants permit uncover- 

 ing in some degree while even a continuous 

 " hilling-up " of most of them during their 

 growth appears to work no harm. 



The dune region of ISTorthern Indiana along 

 the south shore of Lake Michigan, with which 

 the writer is most familiar, has been the sub- 

 ject of numerous botanical as well as general 

 investigations, and has attracted much inter- 

 est recently since the proposal has been made 

 to establish a National Park there. Cowles 

 in a series of interesting papers^ has discussed 

 the plant ecology of the region and Shelford* 

 the animal ecology. 



2 A. D. Hall, "The Soil," p .85. 



s ' ' Ecological Relations of the Vegetation of the 

 Sand Dunes of Lake Michigan, ' ' Bot. Gae., 27, pp. 

 95, 167, 281, 361 (1899). Also "Plant Societies of 

 Chicago and Vicinity," Bull. 2. Greog. Soc. of Chi- 

 cago. 



*' ' Animal Communities in Temperate Americ*, ' ' 

 Bull. No. 5. Geog. Soc. of Chicago. 



The variety of plants in the district be- 

 tween Gary and Michigan City and extend- 

 ing about 1 or IJ miles back from the lake 

 shore is' very great. The storm beach, to the 

 upper limit of storm waves and driftwood 

 (the region of the " singing sands ") prac- 

 tically devoid of vegetation, is usually about 

 40 to 100 feet wide, but naturally varies with 

 the season and wind intensity. There may be 

 a few quick growing annuals such as sea kale 

 (Oahile americana) , bugseed {Corispermum 

 hyssopifolium), etc., in this belt, especially 

 during a few weeks of summer calm. Be- 

 tween the storm beach and the fixed dunes 

 lies the belt of young dunes in the making, 

 and here grow both annuals "and perennials. 

 The sand cherry (Prunus pumila) is here, 

 perhaps of all the most characteristic shrub, 

 but along the same stretch grow red osier 

 dogwood (Cornus stolonifera), cotton woods 

 (Populus deltoides), low willows (8alix glau- 

 cophylla, Salix adenophylla) , artemesia (Arte- 

 mesia caudata). Pitcher's thistle (Cirsium 

 Pitcheri), the grasses, Calamovilfa longifolia 

 (abundant) and Ammophila arenaria (less 

 abundant. Andropogon scoparius {littoralis) 

 does not grow as a rule near the storm beach 

 but higher up on the fixed or partially fixed 

 dunes. 



Back of the storm beach and the embryonic 

 dunes rise the permanent or wooded dunes, 

 well fixed by vegetation, except where blow- 

 outs have cut through and started the sands 

 to drifting once more. In some places the 

 fixed dunes rise abruptly from the rather 

 narrow storm beach, and in others low, 

 moving or semi-fixed dunes run back from the 

 shore for long distances. But the first ex- 

 ample is typical. 



Usually in the region discussed the shore 

 consists of the fine sand described with rela- 

 tively little shingle, but after a succession of 

 severe storms as during the past two years, 

 the amount of shingle increases until the 

 shore is covered with it for a width of ten to 

 forty feet. Undoubtedly this assists in hold- 

 ing the sand and preventing its drifting. 



The sand of the northern Indiana dune 

 region is considerably finer than that of some 



