95^ APPENDIX, BOOK I, 



continuity of the planes which are evident in the divisions which take place 

 in the segments cut off from the apical cell. 

 4. It is probable, contrary to the generally received view, that, in confocal grow- 

 ing-points, the apical cell represents the most slowly growing portion, 

 whereas in non-confocal meristem-protuberances the most active growth 

 may take place at the apex. Westermaier however has come to the con- 

 clusion (Ueb. die Wachsthumsintensitat der Scheitelzelle, Jahrb. f. wiss. 

 Bot., XII, 1 881) that the maximum of increase in volume within the apical 

 region is exhibited either by the apical cell itself or by the youngest 

 segments. 

 Page 140. On the apical growth of Metzgeria furcata, see Goebel, Ueb. das Wachs- 

 thum von Metzgeria furcata und Aneura^ in Arb. d. bot. des Bot. Inst, in Wiirzburg, 

 11. 2, 1879. 



When the segments are cut off from the apical cell by oblique walls these are parts of 

 anticlinals which are completed by the secondary divisions in the adjacent segments (see 

 fig. 150 A), 



Page 146. On growing-points of stems without an apical cell, see Schmitz, Beob. 

 ueb. die Entwickelung der Sprossspitze der Phanerogamen, Halle, 1874. 



Page 147, line 3 from the bottom. It is only in certain cases that the root-cap of 

 Phanerogams is derived from the dermatogen. 



On the structure of the growing-points of roots, see Janczewski, Recherches sur le 

 developpement des racines dans les Phan^rogames, Ann. d. Sci. Nat., ser. 5. t. XX, 1874 : 

 — Treub, Le Meristeme primitif de la Racine dans les Monocotyledones, Leyden, 1876: — 

 Eriksson, Ueb. das Urmeristem der Dikotylen-Wurzeln, Jahrb. f. wiss. Bot. XI, 1878: — 

 Flahault, Recherches sur I'Accroissement terminal de la Racine chez les Phanerogames, 

 Ann. d. Sci. Nat., ser. VI. t. 6, 1878: — Olivier, Rech. sur I'appareil tegumentaire des 

 Racines, Ann. d. Sci. Nat., s6r. 6, t. XI, 188 1. A good account is also given in de Bary's 

 Vergleichende Anatomic. 



From Janczewski's researches, of which the following is a brief abstract, it appears 

 that in many cases there is a distinct meristematic layer, which he terms the calyptrogen, 

 from which the root-cap is derived : — 



Type I. The meristem consists of four distinct layers, Plerome, Periblem, Der- 

 matogen, and Calyptrogen : Hydrocharis Morsus Ranee, Pistia Stratiotes. 

 Type 2. A distinct Plerome and Calyptrogen ; the Periblem and the Dermatogen 

 have common initial-cells : many Monocotyledons (Juncaceae, Haemo- 

 doracesE, Cannaceae, Zingiberacese, Typha, Cyperaceae, Gramineae, Com- 

 melineae, Potameae, Juncagineae, Sagittaria, Limnocharis, Stratiotes). 

 Type 3. A distinct Plerome ; the Calyptrogen, Periblem, and the Dermatogen 

 have common initial cells (Treub) : many Monocotyledons (Liliaceae, 

 Astelieap, Xerotideae, Aspidistreae, Ophiopogoneae, Amaryllideae, Hypo- 

 xideae, Dioscoreae, Taccaceae, Bromeliaceae, Musaceae, Orchideae, Palmae, 

 Pandaneae, Cyclantheae, Aroideae (except Pistia), Irideae, Pontederieae, 

 Sparganium, Butomus, Alisma (?). 

 Type 4. A distinct Plerome and Periblem ; the Dermatogen and the Calyptrogen 

 have common initial cells : most Dicotyledons {Helianthus annuus, 

 Fagopyrum, Raphanus sati'vus, Myriophyllum, Salix, Casuarina stricta, 

 Linum usitatissimum, Primulacese). 

 Type 5. A group of initial cells common to all four layers : some Dicotyledons 



{Cucurbita, Pisum, Phaseolus, Cicer). 

 Type 6. A distinct Plerome and Periblem only ; hence there is no true epidermis 

 or root-cap, these being formed simply by the outer layers of the peri- 

 blem (cortex) : Gymnosperms. 

 Cryptogams. According to the observations of Strasburger (Coniferen und Gne- 

 taceen) and of Bruchmann (Ueb. Wurzeln von Lycopodium und Isoetes, 



