NO. 3 dunkle: plant ecology, channel islands 319 



the examples of this examined by the writer the common species were 

 of a distinctly shrubby habit. The semi-arborescent Quercus dumosa 

 association of Santa Catalina varies from four to six meters (13-19 

 feet), approximately the height of the taller mainland chaparral, while 

 the arborescent Arctostephylos-Photinia-Quercus association of Santa 

 Cruz averages between five and eight meters (16-26 feet). On the 

 four larger islands individual examples of Photinia, Sambucus, Cer- 

 cocarpus, and Prunus may reach a height of twelve meters (40 feet), 

 though Sambucus is only occasionally a component of the chaparral. 



Suffrutescent Plants 



The suffrutescent habit is one of the most characteristic features 

 of the insular vegetation and is much further developed than in main- 

 land communities. The winter season on the islands rarely brings frost. 

 Because of the warmer winters and the more moist summers many 

 perennial herbs do not die back to the surface of the ground during the 

 unfavorable seasons. This condition has perhaps been stabilized by the 

 long period of isolation. To illustrate, Lotus argophyllus has two var- 

 ieties, niveus and adsurgens, which have developed a suffrutescent habit. 

 The suffrutescent species of Castilleja which are endemic to areas of 

 maritime climate are C. foliolosa, C. grisea, C. hololeuca, and C. ana- 

 capensis. In the genus Eriogoniim the following species and varieties 

 are suffrutescent: E. grande, E. grande rubescens, E. arborescens, E. 

 giganteum, E. giganteum jormosum, and E. giganteum compactum. 



Most of the herbaceous perennials on the western headlands are 

 suffrutescent. Here the heavy fogs of summer are driven against the 

 headlands and precipitate an appreciable amount of moisture. On Guada- 

 lupe heavy fogs are condensed upon the trees to such an extent that 

 small streams are formed, which are supposed to give rise to some of the 

 few springs of the island (Eastwood, 1929). 



It has been shown that wind is probably the most important factor 

 in evaporation on the islands. Wind, however, rapidly loses its velocity 

 as the surface of the ground is approached (Lundegardh, 1931). The 

 upper branches of erect shrubs will dry out from wind but those upper 

 branches, even though dead, usually persist and aid in reducing the wind 

 velocity about the base of a plant. This is well illustrated in the case 

 of Coreopsis, whose withered leaves and flower stalks hang about the 

 trunk of the plant until after new foliage has appeared in the winter, 

 and afford a high degree of protection to the trunk and its main branches. 



