NOTES 735 



172. For the earlier literature on vascular bundles, and conducting strands 

 generally, see De Bary : Comp. Anat. Note also Von Mohl : De structure palmarum, 

 in Von Martius : Genera et species palmarum. Id. Vermischte Schriften, L845, 

 p. 129 (Palms). Unger : Ub. d. Ban u. d. Wachstum d. Dicotylcdonenst amines, 

 St. Petersbg. 1840. Nageli : Beitrage Wiss. Bot. No. 1, Leipzig, 1859. Nageli 

 u. Leitgeb : ibid. No. 4, 1867. Dippel : Ub. d. Zusammensetzg. d. Gefassbiindels 

 d. Kryptogamen, Giessen, 1865. Id. Das Mikroskop, 2, 1869. Russow : Mem. 

 Acad. St. -Petersbg., ser. VII., 19, 1872. Id. Betracht. lib. das Leitbiindel- und 

 Grundgewebe, Dorpat, 1878. Schwendener : Das mechanische Prinzip, etc. Leipzig, 

 1874. Von Tieghem : Ann. Sci. Nat., ser. V., 13. Id. ibid., ser. V., 6, 1866. Id. ibid., 

 ser. VII., 3, 1886 (polystely). Id. Bull. Soc. Bot. France, 1886 (Primula). Id. Trade 

 de Botanique, 2nd ed. Paris, 1891, pp. 673 sqq. and 737 sqq. Van Tieghem and 

 Douliot : Ann. Sci. Nat., ser. VII., 8, 1888 (origin of endogenous members). Kny : 

 Ub. einige Abweich. im Baue d. Leitbiindels d. Monocot. Berlin, 1881. G. Haber- 

 landt : Sitzb. Wien, 84, 1881 (collateral foliar bundles of Ferns). Id. P.J. 17, 1886 

 (Mosses). Petersen : Engler's Jahrb. 3, 1882, and Baranetzky : Ann. Sci. Nat., ser. 

 VIII., 12, 1900 (bicollateral bundles). Potonie : Jahrb. Bot. Gart. Berlin, 2, 1883. 

 Leclerc du Sablon : Ann. Sci. Nat., ser. VII., 9, and Zennetti : B.Z. 1895 (Vascular 

 Cryptogams). Heinricher : Ber. 1, 1883, pp. 122 sqq. (Centaurea). A. Fischer : 

 Ber. 1. Ross : Ber. 1, and Reinhardt : P.J. 16, 1885 (anomalous root-structure in 

 Monocotyledons). Mobius : Ber. 5, 1887 (leptocentric bundles). Strasburger : I.e. 

 [157]. Perrot : Journ. de Bot, 11, 1897. H. Fischer : P.J. 35, 1900 (pericycle). 

 Schoute : Die Stelartheorie, Jena, 1903. Scherer : Beih. Bot, Centr. 16, 1904. 



173. As is evident from the text, the terms " conducting strand " and " vascular 

 bundle " are not precisely synonymous. The former is a physiological term, and 

 hence has the wider application ; thus, from a physiological point of view, the simple 

 central strand of a Moss-stem and the complex vascular bundle of an Angiosperm 

 composed of vessels, tracheides, sieve-tubes and hadrome- and leptome-parenchyma 

 are equivalent structures. As regards the significance of the term " vascular 

 bundle," the author adheres to the definition given by De Bary (Comp. Anat. p. 316), 

 who applies it to " strands which consist of tracheae [in the wide sense] and sieve- 

 tubes, as their essential parts." The mechanical strands which so frequently accom- 

 pany conducting strands, are not regarded as belonging to the vascular bundles by 

 De Bary, although that author regards this separation as a convention, so far as 

 descriptive anatomy is concerned (I.e. p. 400). In an anatomico-physiological 

 treatise it is absolutely necessary to keep mechanical and conducting tissues strictly 

 apart. 



The author has found it necessary to substitute the terms "hadrome" (from aSpos, 

 tough, coarse) and " leptome " (from Xeirros, thin, delicate) for the long-established 

 Nagehan " xylem " and " phloem," because the older terminology is strictly topo- 

 graphical in its application, and hence not suited to the needs of the physiological 

 anatomist, Other terms that have been employed [without gaining general 

 acceptance] are Gefassteil and Siebteil [De Bary], and Vasalteil and ( 'rilmtlh 11 

 [Strasburger]. 



[173a. The term ' radial bundle," and the conception of vascular morphology 

 which it implies, have fallen into disuse among British and American botanists 

 since the general acceptance, on their part, in one form or another, of Van Tieghem's 

 stelar theory. According to that theory, the vascular complex which De W,\\\ 

 called a radial bundle (cf. Comp. Anat. p. 319, pp. :U8-366) is. properly speaking. 

 not a bundle at all, but represents the entire stele or central cylinder of the root 

 (or stem) in which it occurs. See also p. 359. ] 



