714 NOTES 



The account of growth by means of apical cells given in the text is based upon 

 the views of Nageli. According to that author's definition, an apical initial is a cell 

 from which all the tissues of an organ can be genetically derived. This definition 

 obviously lays stress upon the individuality of apical cells. 



Strongly divergent views regarding apical cells, and apical growth in general. 

 were held by Sachs. Without entering into details, it may be noted that Sachs 

 looks upon the apical cell as a mere hiatus in the system of intersecting surfaces 

 formed by the cell-walls in the apical meristem ; this negative conception altogether 

 obscures the cell-character of the apical initial and a fortiori ignores its special 

 physiological activity in its role of primordial meristeniatie unit. Cf. Sachs : Arb. 

 Wiirzb. 2, 1878 (arrangement of cells in meristematic tissues). Id. Lectures, 

 pp. 431-459, where there is a very clear exposition of that author's views on the 

 i elations between growth and cell-division. (For a full and critical discussion of 

 Sachs's conception of apical cells, cf. the second edition of the present work, 

 pp. 87 sqq.) 



In addition to Nageli's papers, the following titles may be selected from the 

 extensive literature dealing with growth with the aid of a single apical cell. Cramer : 

 Pflanzenphys. Unters. 3, 1855 (Equisetum). Pringsheim : P.J. 3, 1863 (Salvinia). 

 Hanstein : P..). 4, 1865 (Marsilia). Geyler : ibid. (Sphacelariaceae). Reess : P.J. 

 6, 1867 (Equisetum). Nageli u. Leitgeb : Beitr. wiss. Hot. 4, 1867 (roots). Leitgeb : 

 Sitzb. Wien, 57, 1868 (Eontinalis). Id. Untersuch. lib. d. Lebermoose, 1-6, 1874-81. 

 Russow : Vergl. Untersuch. etc., St. Petersburg, 1872. Pfeffer : Hanst. Bot. 

 Abh. 1, 1871 (Selaginella). Treub : Mus. bot. Leidc, 2, 1877. Strasburger : Botan- 

 ische Praktikum (4th ed.). 1902, pp. 311, 321, 340. RostowzevV : Flora, 73, 1890. 

 Goebel : Organographie, Jena, 1898-1901, p. 448. 



38. Concerning growth by means of several apical cells, especially in Phanero- 

 gams, cf. Schwendener : Sitzb. Naturf. 1879. Id. Sitzb. Berlin, 1885 (apical growth 

 and phyllotaxis). G. Haberlandt : Mittheil. Steiermk. 1881. Dingier : Ub. d. 

 Scheitelwachstum d. Gymnospermenstanrmes. Id. Ber. 1886. Korschelt : P.J. 

 15, 1884. Groom : Ber. 1885. Koch : P.J. 22, 1891 (Gymnosperms). 



Among the authors mentioned, Dingier and Korschelt confidently assert the 

 presence of a single three-sided (pyramidal) initial in the stem-apex of Gymno- 

 sperms, and of Phanerogams generally while all the rest oppose this view with 

 equal determination. 



39. Schwendener's account of the apical growth of the roots of the Marattiaeeae, 

 has been confirmed, so far as essential facts are concerned, by Koch) P.J. 27, 1895) ; 

 but as regards the interpretation of these facts, the latter author follows in the foot- 

 steps of Sachs. Koch has shown that the four apical cells of Angiopteris evecta 

 arise from a single initial by division in two planes at right angles to one another 

 a point of considerable theoretical interest. 



40. Gem ml remarks concerning growth with on, and with several apical cells. Xo 



doubt the presence of several apical cells is often a primitive arrangement, especially 

 among Thallophyta ; for phylogenetic reasons, however, it is probably always to be 

 regarded as a derivative condition among Phanerogams. For these plants aie un- 

 doubtedly derived from Vascular Cryptogams, which almost invariably have a sim;!<' 

 apical cell in each growing-point. We arc thus forced to conclude that the primordial 

 meristem with several apical cells is secondarily derived from that with a single 

 initial, so far as Phanerogams are concerned. In considering how the more complex 

 condition has been evolved, we must pay special attention to any transitional cases 

 that still exist. As a matter of fact, none of these eases (with the exception of one, 

 which will be referred to again later on) illustrate the actual transition from the one- 



