APPENDIX. BOOK I. 
953 
Jena, 1874) the structure of the growing-point of the root of Lycopodium 
is the same as that described above under Type i. 
According to Bruchmann the structure of the growing-point of the root of Isoetes 
agrees with that described under Type 4. 
At the growing-point of the root in the Marattiacese there is a group of several 
large polygonal cells. From these segments are cut off parallel to the base to 
form the root-cap, and internally segments are cut off to increase the Plerome. 
The plerome-segments are further divided by longitudinal walls, and the more 
external of the cells thus formed constitute the cortex, which is differentiated 
at a lower level into Dermatogen and Periblem. These roots are thus inter- 
mediate in their structure between those which have a single apical cell and 
those which have a small-celled meristem. In the case of stems, those of 
certain Selaginellse {arborescens, Per'villei, Wallichii, Lyalli) occupy an analogous 
position. 
Page 149. For a discussion of the physiological causes of the morphological differ- 
entiation of Plants, see Sachs, Stoff und Form der Pflanzenorgane, Arb. d. bot. Inst, in 
Würzburg, II. 3, 1880, and 4, 1882: see also Vöchting, Ueb. Organbildung im Pflanzen- 
reich, 1878, and F. Darwin, The Theory of the Growth of Cuttings, Journ. Linn. Soc, 
XVIII, 1881. 
Page 153. On the Anatomy and Morphology of the Leaf, see J. Chatin, De la 
Feuille, Paris, 1874; and Goebel, Beitr. zur Morphologie und Physiologie des Blattes, 
Bot. Zeitg. 1880 and 1882. 
Page 163, fig. 122. The root represented here affords a good illustration of the 
structure of the apex described above under Type 2 ; it is obvious that the original 
interpretation was the right one, namely, that the root-cap is not developed from the 
dermatogen. 
Page 166. On the development of the lateral roots, see Janczewski, Recherches sur 
le Developpement des Radicelles dans les Phanerogames, Ann. d. Sei. Nat., ser. 5, XX, 
1874. 
In the Equisetaceae the plerome- (bundle-) sheath consists of two layers (Van 
Tieghem), and it is from cells of the inner layer that the lateral roots are developed. 
Line 5 from the bottom. For ' vascular ' read ' xylem.' 
Page 168, paragraph (e). For another case of the conversion of a root into a stem, 
see Goebel, Ueb. Wurzelsprosse von Anthurium longifolium, Bot. Zeitg. 1878. 
Page 170. Wel^/itschia produces two leaves in addition to the cotyledons (see Bower, 
Q^J. M. S. 1881). 
Page 171. It has been found (see p. 400) that the shoots of Equisetacese are not 
endogenous. 
Page 172, paragraph (a). See Heinricher, Ueb. Adventivknospen an der Wedel- 
spreite einiger Farne, and. Die jüngsten Stadien der Adventivknospen an der Wedel- 
spreite von Asplenium bulb'iferum, Sitzber. d. k. k. Wien. Akad. LXXVIII, 1878, and 
LXXXIV, 1881. He finds that in Asplenium the adventitious bud is developed from a 
single superficial cell. 
Page 173, paragraphs (b) and (c). On the adventitious development of organs, see 
Hansen, Vergl. Unters, ueb. Adventivbildungen bei den Pflanzen, Frankfurt, 1881. 
Paragraph (e). It has been shown by Janczewski and by Famintzin that the lateral 
buds of Equisetaceae are not of endogenous origin. 
Page 184, paragraph (d). It is pointed out in Book II that the branching of the 
stem of the Lycopodiaceae is not dichotomous in all cases. 
Page 187. Phyllotaxis. On this subject see Schwendener, Mechanische Theorie 
der Blattstellungen, Leipzig, 1878. According to him the relative positions of lateral 
members depends upon (i) the relative size of the lateral members (when they are deve- 
loped close together), and (2) the increase in length and in thickness of the axis bearing 
them. 
