SOUTHERN EXTENSION OF THE RANGE OF 

 POLYPODIUM SCOULERI. 



By S. B. Parish. 



ALMOST all the California ferns are rupestrine, and possess 

 other characteristics indicative of the aridity, greater or 

 less in degree, with which they have to contend. The 

 most marked exception to this prevailing rule is Polypodium 

 Scouleri. Although this sometimes grows in the soil, its usual 

 situation is the mossy trunks of trees, a habit shared by no other 

 Pacific-coast fern, and restricting its possessor to a climate at once 

 moist and warm. Accordingly it is confined to the coast region, 

 from as far south as Santa Cruz county*, and thence northward 

 into Oregon; its range closely coinciding with that of the redwood 

 (Sequoia sempervirens, Endl. ). This district alone possesses a 

 mild climate in conjunction with a copious rainfall, heavy ocean 

 fogs and humid atmosphere; and by these conditions the conti- 

 nental distribution of this fern is very closely limited. 



But some 250 miles south of the southernmost point which it 

 reaches on the mainland a group of three islands lies within sight 

 of Santa Barbara county, the most distant bearing the name of 

 Santa Cruz Island. Yet further south by 80 miles the island of 

 Santa Catalina is to be seen opposite the coast of San Diego 

 county; and 250 miles beyond, the lonely Guadalope rises from the 

 ocean at a distance of 100 miles from the arid shores of the pen- 

 insula of Lower California. 



The climate of these islands is practically that of the adjacent 

 mainlands. No meteorological observations have been recorded N 

 upon any of them, but it is probable that the atmosphere is some- 

 what more humid, and the fogs heavier, especially on seaward 

 exposures, than on the neighboring coast; yet only in this com- 

 parative way can they be said to be humid or foggy. Certainly 

 they have little, if any, greater share of the winter rains, and 

 their summers, if somewhat cooler, are equally rainless. 



The flora of the islands is of great interest, and may be 

 divided into three groups. The largest group consists of plants 

 identical with those which grow on the neighboring mainland, 

 although in some cases so much more luxuriantly developed as to 

 have received names as varieties, or even as distinct species. 



The second group is made up of a considerable number of 



♦Clark, F. L. Cat. PI. PI. & Ferns Santa Cruz Co., t 3 . 



