American Fern Journal 
Vol. 9 OCTOBER-DECEMBER, 1919 No. 4. 
Water and Mineral Content of an Epiphytic Fern. 
ROLAND M. HARPER 
Current botanical textbooks usually say little or noth- 
ing about the inorganic constituents of epiphytes, and 
tend to leave the impression in the student’s mind 
that most of these plants derive their nutriment en- 
tirely from air and rain, and therefore consist wholly 
of gaseous elements and carbon (whose oxides are 
gases).* But every living organism contains protein, 
and every molecule of protein contains about 2% of 
phosphorus, none of whose compounds are vapors at 
ordinary temperatures, so that they are not found in 
the atmosphere. Furthermore, chlorophyll contains a 
small amount of iron, and the presence of potassium 
in small amounts is supposed to be necessary for the 
formation of starch, so that every green plant must con- 
tain some of these two metals, if not others. 
{Vol Me ne 3 of the JouRNAL, pages 67-98, plates 4 and 5 was issued 
Oct. 11, 9.] 
Exi owledge about epiphytes is summarized very well in 
Schimper’s Plant Geography (English edition, 1903), pp. 197-201, 317- 
329, oe in Cowles’s text-book of Ecology (1911), pp. 511-514, 614-616, 
657-6) 
The ee servations * this paper are intended to apply primarily to the 
io geen of temperate regions, most of which grow on the bark of sb 
eadipoapde no ‘Special ‘organs for ‘Scounieting water or humus. In the 
paeen diversified, includi plants 
that grow in \ large tufts adapted for catching falling leaves and other 
debris, some Dases t rain-water 
and even as a rs omes of small animals, Is, and some that grow in me rove 
vi palm leaves, on smooth barkless trunks of palms an 
m evergreen leaves: and some of the statements made herein ooull. Save 
i be modified to cover all such cases. 
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