244 PLANT ANATOMY. 
other substances (coniine), occurs in peculiarly shaped lines of 
cells in the fruit of the Coniuwm. 
The volatile oil fills, or almost entirely fills, the individual 
cells. ‘The same applies to the mucilage of the mucilage-cells ’ 
(see above), such as are met with, for example, in Rad. Athee, 
in the Orchis tubers, in Cortex Cinnamomi, and in Cortex 
Ulmi. As arule, the cells containing oil or mucilage are some- 
what larger than the cells of the surrounding tissue (Orchis, 
Cort. Cinnamomi,’ Figs. 160, 161, 186 ch). 
As an example of the occurrence or absence of mucilage- 
cavities under special conditions of growth (and therefore by no 
means regularly) we may cite Laminaria hyperborea Foslie (L. 
Cloustoni Edmonston).* 
In addition to volatile oil and mucilage, crystals,‘ tannin ° and 
resin also occur as constituents of true secreting cells. Héhnel ° 
has futhermore shown that kino,’ from the bark of Pferocarpus 
Marsupium Roxburgh, also occurs in extended (100-500 1) 
cells or tubes, united to form long bundles, which are not su- 
berized. On the other hand, the oil-tubes of the Indian species — 
of Andropogon (Andropogon Schenanthus L. was examined), 
from which we obtain the fragrant volatile ‘‘ grass-oils,” * are 
suberized. 
The previously mentioned ‘glandular hairs, the terminal 
1 Berg’s ‘‘ Atlas,” Plate xxiii., Fig. 57. 
? Ibid., Plate xxxvi., Fig. 86 m. 
*M. Foslie, ‘‘ Ueber die Laminarien Norwegens” (Christiania Viden sk.- 
Selsk. Forhandl., 1884, No. 14), p. 47 of the reprint. 
* The true crystals of many plants ‘(especially of monocotyledons), as 
well as the cystoliths, are to be regarded as excretions. 
5 We place the tannic matters here under the excretions, although, like 
the constituents of the laticiferous juices, they probably still partici- 
pate in the processes involving the transmutation of matter. 
* “ Ueber die Art des Auftretens einiger vegetabilischer Rohstoffe in 
den Stammpfianzen.” Sitzungsberichte der Wiener Akademie, 89 (1884), 
January number. 
* To what extent such special substances occurring in the plant are to 
be considered as excretions still remains undetermined. 
__ § Fliickiger, “‘ Pharmakognosie,” p. 157. 
