FORM OF THE PLANT-CELL. 



75 



cans (fig. 86.), and some others, where remarkable substances, such as 

 oil or resin, are present. 



The epidermis of the roots of tropical Orchidece and Aroidece exhibit 

 some very anomalous phenomena. In these cases the stomates lie upon 

 the epidermis, and do not belong to the parenchyma of the bark, but to 

 the root-sheath. The most regular and ordinary form of these internal 

 stomates are seen in Pathos crassinervis, the most complicated and 

 irregular in Aerides odoratum, and in various others they are more or less 

 evident. 



History and Criticism. A knowledge of the functions and structure 

 of the epidermal tissues depends upon accurate observation, which the 

 author of this work was almost the only one to make during the present 

 century. Much misunderstanding has, however, prevailed, and many bad 

 observations have been made. The most important co-workers on this 

 subject have been Krocker, father* and sonf, TreviranusJ, Meyen, 

 Brongniart||, linger.)., and Mohl^f. The view of Brongniart, that the 

 epidermis is a delicate structureless membrane, will be mentioned pre- 

 sently ( 69.). Recently, some botanists instead of using the term stomates 

 have employed the expression skin-glands (Haut-driisen), thus unneces- 



* De Plantarum Epidermide. Halae, 1800. 



f De Plantarum Epidermide. Breslau, 1833. 



{ Beitrage zur Pflanzenphysiologie. Gottingen, 1811. 



Phytotomie, s. 67. || Annales des Sciences Nat. vol. xxi. 



| Die Exantheme der Pflanzen. Wien, 1 833. 



f Ueber die Spaltoffnungen der Proteacea?, N. A. A. L. C. N. C. t. xvi. p. 2. 



85 Epidermis from the midst of the upper leaves of Nelumbium speciosiim, with a 

 stomate. The cells of the epidermis are elevated in the midst into a papilla, which, 

 seen from the surface, appears like a ring. The stomate itself is formed of nine cells 

 of epidermis, and under it lie two stomatic cells of the usual semilunar form. B is a 

 perpendicular section of the same. 



86 A perpendicular section of the surface of the leaf of Aloe nigricans. a, Canal of 

 the stomate, filled with orange-coloured granules of resin, b, Cavity under the stomate 

 lined with cells, which contain granules of chlorophyll and resin. The papillose epi- 

 dermal cells are filled with clear or dark-red sap, and rose-coloured granules of resin. 

 Of the two stomatic cells, one contains chlorophyll, the other a large bright-yellow 

 granule of resin, c, Secretion of the epidermis. 



