APPENDIX. BOOK I. 949 



Sonchus, ^ragopogoriy and Hieracium ; in the cortex of thick-stemmed Cucurbitaceae, such as 

 Cucurbita, Lagenaria, Cucumis, Ecbalium^ and in many species of Potamogeton {P. natansy 

 lucens, pectinatus). 



In Strychnos no sieve-tubes are formed in the secondary phloem, but they occur in the 

 xylem (de Bary. Vergleichende Anatomic, p. 594). 



Page 90. For a full account of the structure of sieve-tubes, and of their transverse 

 connexion, see Wilhelm, Beitr. z. Kenntniss des Siebrohrenapparates Dicotyler Pflanzen, 

 Leipzig, 1880: also, Janczewski, Etudes comparees sur les tubes cribreux, Cherbourg, 

 1881. 



Page 93. On the development of resin-ducts, see Kreuz, Beitr. ziir Entwicke- 

 lungsgeschichte der Harzgange einiger Coniferen, Sitzber. der k. k. Akad. in Wien, 

 LXXVI, 1877. 



Page 98. Stohr (Ueb. Vorkommen von Chlorophyll in der Epidermis der Phanero- 

 gamen-Laubblatter, Sitzber. d. k. k. Akad. in Wien, LXXIX, 1879) has found chlorophyll- 

 granules in the epidermal cells of the leaves of a large number of plants. 



Page 102. Mention should be made, under the head of Stomata, of the water- 

 stomata or water-pores which occur on the leaves of those plants (such as Alchemilla, Zea, 

 many Aroids, Saxifragacese, and Crassulaceae) which excrete drops of water. In some of 

 these an ordinary stoma serves as a water-stoma ; in others the water-stoma is larger than 

 the ordinary stoma, and its guard-cells are incapable of opening and closing the aperture. 

 In the Saxifragacese and Crassulaceae the mesophyll-cells beneath the water-stoma are 

 differentiated so as to form a more or less well-defined mass of tissue, the water-gland, 

 which appears to effect the excretion of saline substances (principally calcic' carbonate) in 

 solution in the excreted water. In each such gland a fibro-vascular bundle terminates. 

 See Gardiner, Quart. Journ. Micr. Sci., 1881 ; also de Bary, Vergleichende Anatomic, pp. 

 55, 113, 389. 



Page 105. On the development of the stomata of Marchantia, see the note above 

 which refers to p. 77. 



Page 106. On Cork, see von Hohnel, Ueber den Kork und verkorkte Gewebe 

 iiberhaupt, Sitzber. d. k. k. Akad. in Wien, LXXVI, 1877. When cork is developed in roots 

 it is formed by the division of the cells of the pericambium, the primary cortex being 

 gradually thrown off. 



Page 108. On Lenticels, see Haberlandt, Beitrage zur Kenntniss der Lenticellen, 

 Sitzber. d. k. k. Akad. in Wien, LXXII, 1875, and Kreuz, ibid.y Entwickelung der Lenti- 

 cellen an beschatteten Zweigen von Ampelopsis hederacea. 



Page 112. In addition to collateral and concentric bundles the following may also 

 be distinguished : — 



1. BicoUateral bundles, in which (as mentioned on page 1 1 1) there is a layer of phloem 



on the inner as well as on the outer side of the xylem; Cucurbitaceae, 

 Melastomaceae, Cichoriaceae, Solanacese, Asclepiadaceae, Apocyneae, Strychnosy 

 Daphne, Eucalyptus Globulus, and probably also Metrosideros, Callistemon, Mela- 

 leuca, Myrtus, and the other species of Eucalyptus, 



2. Radial Bundles, in which the xylem and the phloem strands lie on different radii. 



This arrangement obtains almost universally in roots, exceptions being found 



in those of Dioscorea Batatas, of Ophrydeae, and perhaps in those of Sedum 



Telephium and its allies, in which the bundles are collateral. The bundles 



in the stems of Lycopodiaceae are rather to be regarded as radial than as 



concentric as is done in the text. (De Bary, Vergl. Anat.) 



Page 114. The Fibro-vascular System of Roots. On the transition from the fibro- 



vascular system of the stem to that of the root, see Sophie Goldsmith, Beitr. z. Ent- 



wickelungsgeschichte der Fibrovasalmassen im Stengel und in der Hauptwurzel der 



Dicotyledonen, Diss. Inaug. Zurich, 1876; Gerard, Passage de la Racine a la Tige, Ann. 



Sci. Nat. sen 6, t. XI, 188 1. 



Page 116. The 'vessels' (tracheae) in most plants are really tracheides : this is the 



