July 13, 1900.] 



SCIENCE. 



63 



struction and signification, as well as rela- 

 tively constant in each of the three etymo- 

 logical elements which are used in the 

 composition of such terms, namely, the 

 prepositional, verbal and substantival. 

 A considerable number of terms, derived 

 from the Greek, which have come into use 

 in anatomical and physiological botany, 

 while they have been generally accepted 

 and approved, are sadly wanting in some 

 one or more of these requirements. I al- 

 lude to such terms as heliotropism, geotrop- 

 ism, apogeotropism and diageotropism, 

 which are used with reference to certain 

 plant movements ; and to hypocotyl, epi- 

 cotyl, hyponasty and epinasty, which are 

 used with reference to certain structural 

 conditions. 



The terms geotropism and heliotropism, 

 as first proposed by Frank in 1868 and since 

 used by Darwin and botanists generally, are 

 intended to designate respectively the act 

 of the radical portion of plants in turning 

 downward, or toward the earth, and that of 

 the stemmate portion in turning upward, or 

 toward the sun ; but in neither case is this 

 accepted signification etymologically the 

 true one. Geotropism being derived from 

 yvj, the earth, and rpoTzo?, a turn, or turn- 

 ing, literally signifies earth-turning ; and 

 heliotropism, being derived from ip-co^, the 

 sun, and rpoTro?, similarly signifies sun- 

 turning. That is, because they are each 

 composed of verbal and substantival ele- 

 ments only, the prepositional element being 

 omitted, their conventional signification is 

 really far-fetched. Long before either 

 Frank or Darwin used these terms in their 

 present conventional sense, the term helio- 

 trope was used to indicate the habit of the 

 flowering parts of certain plants in facing 

 and following the sun in its daily course. 

 This act being really synheliotropism, or a 

 turning with the sun, is quite different from 

 that which Frank indicated by bis special 

 use of the old term. It seems to have been 



for this reason that Darwin happily pro- 

 posed in its stead the term apogeotropism, 

 and for the first time introduced the neces- 

 sary prepositional element in the construc- 

 tion of this class of botanical terms. 

 Strangely, however, although he at the 

 same time also employed that element in 

 the construction of his term diageotropism, 

 he failed to add it to Frank's term geotrop- 

 ism, which should have been written epi- 

 geotropism* to make it strictly correlative 

 and antithetic with apogeotropism. These 

 two terms, when made to contain three 

 elements each, are appropriate for the use 

 intended because they signify and fully ex- 

 press the acts of turning toward and from 

 the earth without reference to the sun as 

 the assumed objective point of direction. 



Before either Frank's or Darwin's incom- 

 parable works containing these and related 

 terms reached America I had, as Professor 

 of ' natural history ' at the Iowa State Uni- 

 versity, constructed and personally used in 

 my lectures the terms epitropism and apo- 

 tropism in the same manner and for the 

 same purpose that Frank's geotropism and 

 Darwin's apogeotropism are respectively 

 used. These terms I derived from Greek 

 prepositional and verbal elements only, 

 namely ^jti', toward, a-u, from, and rpuT:o<s, 

 a turning omitting the substantival element 

 jri, the earth. Because they are thus shorter 

 and more conveniently useable in their 

 adjective and adverbial forms they seem to 

 be preferable to Frank's and Darwin's cor- 

 responding terms, even if the former should 

 be amended by adding the prepositional 

 element. While the omission of either the 

 prepositional or verbal element from such 

 terms as these is a real defect, the omission 

 of the substantival element from apotropism 

 and epitropism does not in the least obscure 



* While it is true that the radical signification of 

 the Greek preposition k-Ti is upon, it is often, and no 

 less properly, used as equivalent with the English to, 

 or towards. 



