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ECOLOGY 



nized epidermis is as effective in keeping water out as in keeping it in. Recently 

 it has been shown that such salt-containing plants as Salicornia are able to absorb 

 water somewhat readily through the aerial organs. Though adequate experiment 

 is lacking, there is some reason for believing that the leaf sheaths of many grasses 

 and umbellifers and the cup-shaped leaf bases of Silphium perfoliatum have some 

 absorptive efficiency. 



Water absorption in epiphytes. Thallophytes and bryophytes. In 

 regions with cold winters true epiphytes are confined essentially to the 



FIG. 903. A live oak (Querctis virginiana) festooned with the long moss (Tillandsia 

 usneoides}, an epiphytic member of the pineapple family, which absorbs liquid water by 

 means of specialized scale hairs ; Tampa, Fla. Photograph by E. W. COWLES. 



lower plants, and in these groups absorption is dominantly a function 

 of chlorophyll-bearing organs rather than of rhizoids. The widespread 

 distribution of these plants in exposed situations is due in large part to 

 their ability to endure prolonged desiccation, since they quickly lose most 

 of the absorbed water by transpiration through the surface by which it en- 

 tered. Among such xerophytic epiphytes are some algae (as Pleurococcus) 

 and liverworts (as Frullania) and many mosses (notably Orthotrichum), 

 but the most representative epiphytic group is that of the lichens. 



