3i6 



The Ohio Naturalist. 



[Vol. VIII, No. 6, 



Station at Sandusky, about three miles distant across the Bay 

 was 79 degrees, Fahr. (At 1 inch above the surface of the soil 

 the air was 118 degrees; at 6 inches, 89; at 12 inches 84, — ther- 

 mometer properly shaded.) 



Thus far the vegetational structure in the succession under 

 consideration has been comparatively uniform over the entire 

 Sand Plain wherever the latter may be situated on the peninsula, 

 but the Artemisia-Panicuni Formation may be invaded and 

 eventuallv succeeded by a formation having distinctly northern 

 phvtogeographical relationships, or, on the other hand, the 

 succeeding formation may be one of more southern affinities. 



Fig. 7. Small area of Sand Plain enclosed by Quercus velutina and Q. 

 imbricaria, Celtis occidentalis. Note communities of Opuntia humifusa 

 with scattering Artemisia, Panicmn virgatiim, P. scribncrianum and 

 Verbascum thapsus. 



In the work on Presque Isle the writer found a considerable differ- 

 ence in both the habitat and in the corresponding vegetation in 

 different portions of the Sand Plain such that two formational 

 series could be distinguished as early in the succession as the 

 Drift Beach. On Cedar Point, however, there are no such evi- 

 dent distinctions early in the succession but the critical period 

 appears to be in the sand plain stage. 



Accordingly, the succeeding vegetational structures with a 

 more southern phytogeographical relationship will first be taken 

 up, after which the structures of northern affinities will be dis- 



