180 THE PLANT WORLD. 



Parmellan are by uo means so common un the islands as they are 

 in the Mississippi Valley and eastward, and our common Leca- 

 nora suhfu.sca of the eastern United States is replaced almost 

 entirely on these islands by Lecanora pacifica, which aboimds 

 everywhere on bark, living and dead. Rhizocarpon geographi- 

 cum is very common on dry rocks, and with its bright greenish 

 or yellowish crust, will always attract the attention of students 

 who visit the Archipelago. Closely related to this lichen and 

 as common is Ehizocarpon petraeum, which is not so easily seen 

 because of its dull color. 



There is an excellent opportunity for the study of lichen 

 formations on these islands, but such work must be done by one 

 who is very familiar with the lichen flora of the region and conse- 

 quently not during the first summer's study. The most conspic- 

 uous lichen near the Station is Ramalina reticulata, which covers 

 some of the trees after the manner of some of the longer Usneas 

 cf the coniferous woods of Michigan, "Wisconsin and Minnesota. 

 This BamaJiiKi is, with its reticulated structure, a most beautiful 

 plant, which will always attract attention in the region. The 

 Cladonias of the islands are very interesting, and there are many 

 most excellent formations of them. With the Cladonias on 

 the rocks, often grows Pilophorus cereolus, which with its erect 

 habit is easily mistaken for a Cladonia. For the student of 

 lichen ecology there are the damp and deeply shaded woods, the 

 more open woods, the common matamorphic rocks in the woods 

 and those along the shores and drier places, the sandstones and 

 limestones in limited areas, deciduous and coniferous trees, vari- 

 ous conditions of soil and various altitudes from the sea level to 

 2,409 feet. Also various sizes of islands may be found, from 

 the smallest reefs, with a few rock-loving lichens growing on 

 the portions of the reef above high tide, to those ten or more miles 

 in length and for the most part more or less densely wooded, ex- 

 cept in places where the ground has been cleared and is being 

 used for agricultural purposes. 



