85 



(io-2om.) high, making it much deeper than any in the inland dunes 

 of IlHnois. Developing in the midst of moving sand, they may have 

 a different structure and different plant associations from those of 

 the inland regions. 



Rydberg (i8p^j: 135) described blowouts in the sand-hill region 

 of Nebraska which were 100 yards (100 m.) in diameter and from 

 50 to 60 feet (15-20 m.) deep. He mentioned how sand slides down 

 from the sides into the basin, but did not describe similar behavior 

 of the vegetation. Certain grasses, as Calamovilfa longifolia, Red- 

 iieldia flexuosa, Bragrostis trichodes, and Muhlenhergia tenuis, col- 

 onize in the basin and take part in the stabilization of the blowout. 

 Of these four grasses, Calamovilfa and Bragrostis live also in the 

 Illinois sand region, but not in blowouts. Rydberg's work was mainly 

 taxonomic in its aims, and the ecological notes which he gives are 

 merely incidental. 



Pound and Clements {1^00: 365-368) later studied the same re- 

 gion from an ecological standpoint, and have given the best descrip- 

 tion of blowouts and their vegetation. Rcdiieldia flexuosa and Miili- 

 lenbcrgia pungcns are "habitually and almost exclusively blowout 

 inhabitants." These two gTasses are pioneers in binding the sand and 

 creating conditions suitable for other plants. Stabilization appar- 

 ently begins at the bottom, and ultimately the whole blowout is re- 

 occupied by the bunch-grass vegetation. The description does not 

 give an idea of the structure or vegetation of the other parts of the 

 blowout, which are probably the same in Nebraska as in Illinois. In 

 an earlier paper {i8pS: 392) Pound and Clements described the 

 Nebraska blowouts in a short paragraph, and indicated that the life 

 of a blowout from formation to stabilization may be about ten years. 

 In both papers the "sand-draw" formation is also described {i8p8: 

 392; IQOO: 368-370). In neither case does the description give a 

 clear idea of the vegetation or the environmental conditions, but it 

 seems probable that the vegetation is somewhat similar to the blow- 

 sand association of this paper. No similar habitat occurs in Illinois. 



Jennings {rpo8: 324-326) has described blowouts on Cedar 

 Point, near the western end of Lake Erie, which extend down to a 

 former surface level, or fossil beach. On them there is developed 

 sometimes a heath vegetation of Arctostaphylos Uva-nrsi and Ju- 

 niperiis, and sometimes an association characterized by Artemisia 

 caudata and Panicnm virgatum. The complex nature of the blow- 

 outs was recognized but the successions which led to their stabiliza- 

 tion were not worked out. In a later paper on the veg'etation of 

 Presc|ue Isle (ipop: 313-318) Jennings regards his Artemisia-Pam- 



