NO. 3 dunkle: plant ecology, channel islands 317 



At all times of the year there appears to be a gentle shoreward 

 drift of surface waters toward the southern California coast (Leconte, 

 1888). Thus driftwood is found on the southern and western beaches 

 of most of the islands, the northwestern on San Miguel, and rarely on 

 the eastern and northern beaches. Such driftwood as is found consists 

 mainly of material from vessels and debris carried to the ocean by the 

 streams of central and northern California. If these conditions have 

 prevailed in past geological periods it is highly improbable that plants 

 could have migrated from the southern California coast to the islands 

 by means of ocean currents. 



VI Life-forms of Island Plants 



The life-forms of the island plants seem principally those which 

 best enable the plants to survive the long, unfavorable season of summer 

 and fall. The modifications which have been evolved to meet this un- 

 favorable season are not greatly different, in most respects, from those 

 generally seen in plants of the Mediterranean climate. However, the 

 maritime climate differs definitely from the Mediterranean types present 

 in interior cismontane southern California. Accordingly it may be 

 expected that there will be corresponding differences in the growth 

 forms of the two regions. 



Plants adapted to the Mediterranean type of climate are marked 

 by sclerophyllous foliage for trees and shrubs, and by a high percentage 

 of therophytes (annuals), hemicryptophytes (perennial herbs and low 

 suffrutescent semi-shrubs), geophytes (plants with bulbs, tubers, or 

 rhizomes), and chamaephytes (suffrutescent shrubs and low woody 

 shrubs). Maritime plants and those of xeric conditions sometimes 

 develop a succulent form (Raunkiaer, 1934). On the islands a stronger 

 maritime influence, the oceanic type of climate, has accentuated the 

 development of certain of these characteristics. In order to understand 

 better the modifications which have taken place it will be advisable to 

 examine the island forms in some detail. 



Very few deciduous shrubs or trees are to be found on any of the 

 islands except Santa Catalina, Santa Rosa, and Santa Cruz. Even here 

 they rarely play a dominant role, and then only in very limited riparian 

 areas. Populus and Salix are on all three of these islands, and Acer 

 macro phyllum is occasionally met on Santa Cruz. Two herbaceous 

 shrubs are exceptions to the hard-wood shrubs and are more typical of 

 moist, subtropical conditions. These shrubs, apparently formerly much 

 more abundant, are Coreopsis gigantea and Lavatera as surgenti flora. 



