APPENDIX. BOOK I. 
949 
Sonchus, 'Tragopogon, and Hieracium ; in the cortex of thick-stemmed Cucurbitaceae, such as 
Cucurbita, Lagenarta, Cucumis, Ecbalium, and in many species of Potamogeton (P. natans, 
lucens, pectinatus). 
In Strychnos no sieve-tubes are formed in the secondary phloem, but they occur in the 
xylem (de Bary, Vergleichende Anatomie, 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 Siebröhrenapparates Dicotyler Pflanzen, 
Leipzig, 1880: also, Janczewski, Etudes compar6es sur les tubes cribreux, Cherbourg, 
1881. 
Page 93. On the development of resin-ducts, see Kreuz, Beitr. ziir Entwicke- 
lungsgeschichte der Harzgänge einiger Coniferen, Sitzber. der k. k. Akad. in Wien, 
LXXVI, 1877. 
Page 98. Stöhr (Ueb. Vorkommen von Chlorophyll in der Epidermis der Phanero- 
gamen-Laubblätter, 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, 7^ea, 
many Aroids, Saxifragaceae, and Crassulacese) 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 Saxifragaceae 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. Sei., i88i ; also de Bary, Vergleichende Anatomie, pp. 
55, 113, 389. 
Page 105. On the development of the stomata of Marchantia, see the note abov^ 
which refers to p. 77. 
Page 106. On Cork, see von Höhnel, Ueber den Kork und verkorkte Gewebe 
überhaupt, 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, Beiträge zur Kenntniss der Lenticellen, 
Sitzber. d. k. k. Akad. in Wien, LXXII, 1875, ^i^d Kreuz, ibid., Entwickelung der Lenti- 
cellen an beschatteten Zweigen von Ampelopsis heder acea. 
Page 112. In addition to collateral and concentric bundles the following may also 
be distinguished : — 
1. Bicollateral bundles, in which (as mentioned on page iii) there is a layer of phloem 
on the inner as well as on the outer side of the xylem ; Cucurbitaceae, 
Melastomaceae, Cichoriaceae, Solanaceae, Asclepiadaceae, Apocyneae, Strychnos, 
Daphne, Eucalyptus Globulus, and probably also Metrosideros, CalHstemon, 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. Zürich, 1876; Gerard, Passage de la Racine ä la Tige, Ann. 
Sei. Nat. sen 6, t. XI, 1881. 
I'age 11Ö. The ' vessels ' (tracheae) in most plants are really tracheides : this is the 
