Jennings : A Botanical Survey of Presque Isle. 313 



forms of the plants. Among other such adaptations are mentioned 

 the trailing form of SiropJwstyles helvola, and the radiant form of 

 Cakile edeniiila and of Euphorbia polygonifolia. On the drift-beach 

 at Presque Isle Xanthium, ordinarily, and Cetichrus, often, shows the 

 radiant life-form. This form is chiefly exhibited by annuals with a 

 well defined tap-root and a stem branching immediately above the 

 surface of the ground, the lower branches, at least, lying on the sur- 

 face of the ground and spreading radiately like the spokes of a wheel. 



As Kearney further suggests, the trailing and radiant forms are 

 better fitted by their closely appressed lower branches to shade the 

 soil, thus conserving its moisture, and also to prevent undue ex- 

 posure to the heat and light reflected from the sand beneath, as well 

 as to prevent so free a circulation of air through the foliage. In this 

 way transpiration is probably considerably lessened, and on account 

 of the protection afforded by the form of the plant the soil is not so 

 readily blown away from the roots by the wind. 



Succulent leaves are, of course, a further protection against excessive 

 transpiration and the injurious effects of high insolation, and it is to 

 be noticed that such leaf-forms are almost a universal characteristic of 

 the plants of the Cakile-Xanthiiim formation. This leaf- form is 

 further accompanied by light-colored, insolation-reflecting foliage in 

 Cakile, Xanthium, Eiipho7'bia, and to some extent in Strophostyles. 



The Sand-plain. — The Artemisia-Paniciwi Formation. 



At the eastern end of the peninsula, extending above and beyond 

 the drift -beach, is an area of between two and three square miles of 

 dry, comparatively level sand-plain, which has been gradually built up 

 by drifting sand as the beach has been formed farther and farther 

 lakeward. Towards the southeast this sand-plain contains a number 

 of lagoons or ponds, and is more prominently strewn with logs and 

 driftwood, but from the immediate vicinity of the Key Post, and 

 extending towards the north and west, the sand has been drifted in so 

 abundantly as to have filled the ponds and to have buried the drift- 

 wood (see Plate XXVII), the surface thus presenting here a uniformly 

 level plain with the exception of a few small sand-ridges and dunes. 

 It is this latter portion of the sand-plain which is to be considered in 

 connection with the succession under discussion. The two portions 

 of the sand-plain are, of course, essentially similar in their physio- 



