229 



valley, northern Illinois, about eighty miles northwest of Peo- 

 ria. Collections in the Illinois River area are cited from Tehe- 

 ran, at the eastern border of this area, fifteen miles east of Ha- 

 vana, from Pekin,ten miles below Peoria, from Matanzas Lake, 

 eight miles below Havana, and from the sand beach of Thomp- 

 son Lake, in Fulton county, opposite Havana; but especially 

 from six principal regions in the vicinity of Havana, desig- 

 nated by numerals. Those who care for topographical rather 

 than geographical detail may note that H.l, 2, and 3 are the 

 three principal blow-sand areas, counting from north to south 

 and in order of sandiness; that H.3 has a large admixture of 

 areas of black-jack growth; that H.4 and 5 represent forest on 

 sand; 4, the newer growth (black-jack), with some open ground; 

 and 5, the older and more varied forest, approaching ordinary 

 Illinois forest conditions with a little open sandy ground; and 

 that H.6 is the immediate sandy river beach and lake beach 

 along the western margin of the sand plain. For convenient 

 reference, the principal details with regard to these various 

 localities are summarized as follows: 



H.l = the Devil's Neck, ten miles north of Havana, open 

 land, a large area of barren sands and blowouts, approached by 

 sandy roads. (See p. 197, and PI. XII., Fig. 1; XIV., Fig. 1; 

 XX., Fig. 1.) 



H.2 = the Devil's Hole, two miles east of Havana, similar 

 to H.l but smaller. (See PI. XIII.; XIX., Fig. 1; XX., Fig. 2.) 



H.3 = a large area of rolling sand-hills with occasional 

 blowouts, considerable waste sandy open land, and areas of 

 scrubby black-jack forest, lying south and southeast of Havana. 

 (See PL Vm -XI., XV.-XVII.) 



H.4 = the east margin of the sandy postglacial island north- 

 east of Havana near the center of which is the Devil's Neck. 

 This margin is mostly covered with black-jack. (See PL 

 XXL, Fig. 1.) 



H.5 = the marginal sand ridge just above Havana, mostly 

 covered by comparatively well-developed forest growth. (See 

 p. 198, and PL XXL, Fig. 2.) 



