EPIDERMIS. lOI 



without any specially remarkable arrangement of the cells. In the Utricularias the 

 digestive function may be carried on by the four-armed hairs already mentioned 

 (p. 62), which are seated in large numbers on the inner surface of the sacs which 

 catch animals. In the investigated species of Drosera, and in Drosophyllum, the 

 form and arrangement of the cells on the secreting leaf-teeth is exactly like those of 

 the circumscribed dermal-glandular spots, occurring especially on the teeth of the 

 foliage-leaves. The description of them for Drosera will be better given below 

 (Chap. VIII) in connection with that of the endings of vascular bundles. 



The presumptive digestive glands of Nepenthes ^ so often investigated, but lately 

 very thoroughly treated of by Wunschmann, have the most peculiar arrangement. 

 They are situated in these plants on the middle and lower portion of the pitcher- 

 shaped part of the leaf, on the inner surface, in many species also on the inner surface 

 of the lid. They belong to and arise from the epidermis, and consist of a disc- 

 shaped basal portion, formed of one small cubical cell : this bears a rounded head, 

 composed of prismatic thin-walled cells, arranged in a perpendicular, radiate manner. 

 Their whole form is thus that of a globular wart. Each of these very numerous 

 warts, which can even be recognised with the naked eye, lies in the pitcher in a 

 pouch opening into it : the pouch is formed by extension of the row of epidermal 

 cells surrounding the upper margin of the wart in the form of a semicircular sharp- 

 edged band, which is drawn forward as a cap over the wart. On the lid of the 

 pitcher this band is equally high all round. In the upper part of the pitcher the 

 glands are absent from the inner surface : the epidermis is here covered with granules 

 of wax in a simple layer, and is smooth, excepting that numerous small semilunar 

 hair-cells (concave on the under side) are inserted between the slightly undulating 

 epidermal cells. On Sarracenia, compare p. 69. 



With all the similarity of structure of the digestive organs in question to that of 

 the above-described dermal glands, they differ in structure fundamentally from these 

 in this point, that their secretion — and also, as far as investigation extends, the mu- 

 cilage of Drosera and Pinguicula — does not appear in the wall, between the cellulose 

 wall and cuticle, but on the free outer surface of the latter. 



Other generally remarkable, anatomical peculiarities cannot at present be brought 

 forward, without far transgressing the boundaries here imposed, and entering deeply 

 into physiological details. Here therefore, after this short notice, we can only refer to 

 the recent literature on insectivorous plants, and a few older works on the anatomy 

 of the glands in question, some of which have been already cited. 



Ch. Darwin, Insectivorous Plants, London, 1875. — J. D. Hooker, Address to the Dep. 

 of Zoology and Botany of the Brit. Association, Belfast, 1874. — F. Cohn, Ueber die 

 Blasen von Aldrovanda und Utricularia, Beit. z. Biologie, Heft HI. p. 71. — Treviranus, 

 Meyen, Oudemans, Wunschmann, /. c, Schacht, I.e., Utricularia, comp. p. 62. — E. Morren, 

 Note sur le Drosera binata, Bull. Acad. Belg. 1875. — Aldrovanda, Cohn, Flora, 1850. — 

 Caspary, Bot. Ztg. 1859, P- 1 17) &c. — Fraustadt, Anatomic d. Dionsea muscipula, in Cohn, 

 Beitr. z. Biol. d. Pfl. Bd. H. p. 27. — Fr. Darwin, The process of aggregation in the tentacles 

 of Drosera rotundifolia, Micr. Journ. vol. XVI. N.S. — Warming, in Videnskab. Meddel- 

 elser fra nat. Forening i Kjobenhavn, 1872, p. 168, (French Resume, p. 18 ; Drosera). 



1 Treviranus, Zeitschr. f. Pkysiologie, III. p. 73. — Meyen, Secretionsorgane. — Oudemans, De 

 Bekerplanten, Album d. Natuur, Groningen, 1863 and 1864. — Wunschmann, Ueber d. Gattung 

 Nepenthes, Diss. Berlin, 1872. 



