Plant Societies of Monterey Peninsula. 



81 



of nitrogen, and over which there plays almost constantly 

 the salt laden spray of the ocean. 



If we consider the various plant zones in their logical 

 order, the one following naturally upon the rock formation 

 is that of the sand-dunes. These dunes of the Monterey 

 Peninsula occur at three different points, marking the posi- 

 tion of the beaches of varying extent, and in each case 

 limited on the leeward side by the pine forest that extends 

 over the greater part of the peninsula. The plants 

 that constitute the sand-dune flora, like those 

 peculiar to the rock formation, must be able to thrive in soil poor 

 in nitrogen and in organic detritus. They must also be able to 

 adjust themselves to very material changes resulting from severe 

 winds and torrential rains. Not infrequently, too, during heavy 

 storms at sea, the atmosphere sweeping in over a sand-dune is 

 charged with ocean spray, and such plants as do not take kindly 

 to a suffusion of brine are not likely to find a congenial place in 

 sand-dune society. 



Those species that may be regarded as typical dune plants 

 are not numerous; but associated with them are several plants 

 found among the pines, along the ocean shore, or even certain 

 species that commonly occur in the chaparral formation. The 

 species characteristic of the sand-dunes include two species of 

 the sand verbena, Abronia latijolia and A. umbellata, the sea fig, 

 Mesembryanthemum aequilaterale, Franseria bipinnaiifida, 

 CEnothera ckeiranthifolia, Convolvulus soldanella, Corelhrogyne 

 filaginijolia leucophylla. 



Aside from such plants as typify sand-dune vegetation are 

 many species of mesophytes that after repeated generations 

 have developed along xerophytic lines until they are thoroughly 

 capable of maintaining themselves under conditions quite 

 inimical to the same species in a normal mesophytic environment. 

 This has been made possible in part by the gradual modification 

 of organs, principally the leaves, sometimes by a marked reduc- 

 tion in leaf surface, or by the excessive growth of protective 

 hairs, and in some cases through the adoption of a prostrate or 

 procumbent habit, as in the case of CEnothera ckeiranthifolia and 

 in Corelhrogyne filaginijolia leucophylla. Many, if not all, sand- 



