EPIDERMIS. 



69 



often described club- or egg-shaped warts of Dictamnus, which end in a short hair, 

 there are found cell-contents of a character exceptional for epidermal structures. The 

 cells finally fuse to form intercellular balsam-containing cavities '. These, as Rauter has 

 carefully shown, are multicellular bodies derived from a single epidermal cell, consist- 

 ing of a permanent peripheral layer of epidermal cells with scanty contents, running 

 out into the terminal hair, and an inner multicellular mass. The cells of the latter 

 contain, about the end of their growth, at first chlorophyll ; then there appear drops 

 of resin and ethereal oil in increasing quantity ; these finally unite to large drops, 

 which fill the cavity formed by the solution of the inner cell-walls (comp. Fig. 22). 

 Beneath the epidermis, but derived in part from it, there arise in Dictamnus similar 

 cavities containing ethereal oil. INIartinet 

 {I.e. page 176) describes in Cuphea lanceo- 

 lata long, multiseriate, shaggy hairs con- 

 sisting of elongated cells : in the broad base 

 of each of these is enclosed a central round 

 body consisting of many small isodiametric 

 cells. This resembles the central tissue of the 

 warts of Dictamnus in its position and its 

 contents, which apparently include drops 

 consisting of ethereal oil : but the solution of 

 the cell-walls, which occurs in the latter case, 

 was not observed in the former. Peculiarly 

 formed groups of cells, characterised by their 

 dense contents, which turn brown on drying 

 or treating with alkalies, and which pro- 

 trude little or not at all above the outer sur- 

 face, and only slightly inwards, occur in num- 

 bers in the epidermis of the tubular leaf of Sar- 

 racenia -. They are globular, or flask-shaped, 

 with the neck directed outwards, and consist 

 of about 16 small cells derived apparently 

 from the division of one epidermal cell. Their 

 structure has been well described by VogI 

 from dried material. Their origin and sig- 

 nification remains still to be investigated. 



Those cells and cell-groups belonging to 

 the epidermis, which have contents of peculiar !!"'°"5\^ '"^'"'■'^ specimen. After Rauter. from sachs- 



^ ' '^ Textbook. 



nature, such as in the above examples, are 



often described as glands if they are also characterised by special form. This 



term will be discussed in Sect. 19. 



Air-coniaining dry hairs, scales, or shaggy hairs, form dry opaque coverings 

 which appear of difi"erent colour according to the character of the membranes and 



1 Fig. '22. — Dictamnus fraxiiieUa ; oil-containing dermal 

 warts, cut perpendicular to the surface. A youngest stage 

 of development ; B rather older ; C (020) median section 



* Meyen, Secretionsorg. Taf. I. pp. 28, 29. — Unger, Anat. und Physiol, p. 212. — Hofmeister, 

 Handb. I. p. 259. — Rauter, Martinet, I.e. 



^ A. VogI, Phytohistolog. Beitrage. Sitzgsber. d. Wiener Acad. Bd. 50 (1864). 



