Jennings: A Botanical Survey of Presque Isle. 311 



The Drift-Beach. — The Cakile-Xatithium Formation. 



The drift-beach (see Plate XXVI) extends from the upper limit of 

 the lower beach, /'. <?., the upper limit of the waves of summer storms, 

 to the upper limit of the waves of winter storms. It thus comprises 

 a zone immediately above the lower beach and differing from it in that 

 it is not exposed to the mechanical violence of the surf during the 

 growing season. Like the lower beach it is composed of loose, clean 

 sand, but it is marked by a considerable accumulation of driftwood — 

 whence its designation here as the drift-beach. This habitat is well 

 developed at the eastern end of the peninsula and is quite well shown 

 along the northern shore, except at the western end near the Head, 

 where the shore is receding and the lower beach extends back to the 

 base of a low vertical sand cliff. 



This drift-beach is essentially synonymous with MacMillan's ";///>/- 

 strand,'"^'" Schimper's "■mid-shore,'' '''^ Cowles's '' middle beach'' '^'^ 

 and Ganong's " new beach." ^* 



The drift-beach, at least in its surface layers, constitutes an ex- 

 tremely xerophytic habitat. The loose white sand is exposed to the 

 full force of wind and sun and the surface at times becomes very dry 

 and hot, but as quickly loses its heat when insolation ceases. The 

 water-table is but a short distance below the surface and damp sand is 

 always to be found by digging down a few inches. If a plant can 

 survive until its roots get down a few inches, there need be no lack of 

 water from that source, but it seems probable that most of the plants 

 whose disseminules may reach this habitat are unable to exist until 

 their roots have reached the damp sand below. Following Clements 

 this habitat may be termed dissophytic , being xerophytic above the 

 surface layers of sand and mesophytic or even hydrophytic below. 



The drift-beach is occupied by a formation, which from its compo- 

 sition will be termed the Cakile-Xanthiiim Formation. The habitat 

 being exposed to the mechanical violence of the surf during the 

 winter, the formation consists entirely of annuals, and in response to 

 the dissophytic conditions the plants are xerophytic, at least in their 

 aerial portions, most of them being more or less succulent. 



^5 MacMillan, Conway. /. c. , pp. 969-973. 

 36Schimper, A. F. W. /. c., p. 180. 

 ^'Cowles, H. C. /. <r., pp. 11 5-1 17. 



'^Ganong, W. F. "The Nascent Forest of the Miscou Beach Plain.'' £ot. 

 Oaz.,42: 85-87. August, 1906. 



