1922] _ THONE—STARVED ROCK 349 
the sandstone cliff, also clayey; (3) exposed edge of cliff, sandy or 
sand mixed with clay and shale; (4) precipitous cliff, usually with 
weathered crevices and shelves; (5) talus slope, generally very 
sandy, with much humus and some clay; (6) canyon bottom (allu- 
vial), or river terrace — to sandy), or juvenile floodplain 
(alluvial). 
Veter rion 
With so varied a terrain as that just outlined, presenting such 
widely diverse types of habitat, it is only natural to expect a very 
widely diversified vegetational development. This expectation is 
well realized, for within the limits of the scant thousand acres of the 
Starved Rock State Park there is a collection of plants that for 
floristic and ecological interest can hardly be matched. All the 
orthodox successional stages between Quercus macrocarpa of the 
prairie edges and Q. velutina of the upland woods, to Q. bicolor of 
the sloughs and the Populus-Salix thickets of the river edge are there 
as a matter of course; but the region offers all the groups of dis- 
juncts mentioned in a preceding paragraph as well. There are 
places in this park where one can stand beside a white pine and 
throw a stone through the top of a pawpaw! 
No attempt can be made in this place even to outline the vege- 
tational types to be found in this region. This has been presented 
briefly by Cow.es (6), and a more detailed description by the present 
writer is now in preparation. The present study concerns itself 
more with the physical fagtors of the environment, especially as they 
affect seedling growth and hence succession, in a number of typical 
locations in the park. Ideally these determinations should have 
been made in a considerable number of places, at least three for 
each clearly distinguishable type of association, but this was beyond 
the available resources in time and apparatus. In all, seven sta- 
tions were maintained throughout the major portion of one growing 
season, two on the upland, three on talus slopes, and two at the 
bottom. In locating these, some diversity was possible, overcoming 
in at least a slight degree the unavoidable inadequacy of data. 
Stations 7 and 6 were located on the upland, no. 7 on the upland 
proper, in a second growth Quercus velutina-Q. alba-Carya ovata 
association, and no. 6 on a gentle slope from this toward the edge 
