ANATOMY AND PHYSIOLOGY OF PLANTS. 225 



21. Bauer, on the contrary, conceives the structure 

 to be altogether cellular, and varying in different plants. 



So far as the experiments go, which have been instituted with a 

 view of ascertaining the structure of the epidermis, we must admit 

 the presence of cellular structure, and also he assured of the various 

 results which have ensued from different experiments on the epider- 

 mis of different parts of a plant, and also on the epidermis from the 

 same plant, but at another period of its growth. 



22. Dr. Thomson joins his opinion with the elder 

 Saussure, that the epidermis is a fine, transparent, unor- 

 ganized pellicle. 



In their idea of this texture, the pores, by which the insensible 

 perspiration escapes, are so minute, that they are quite invisible, 

 and with difficulty permit the passage of air through them. 



23. Saussure describes it, as constituting a bark of 

 two layers ; the interior layer composed of a net- work, 

 which he calls the cortical net-work, interspersed with 

 a multiplicity of what he calls cortical glands, and the 

 exterior layer consisting of a fine and transparent mem- 

 brane, which he regards as the true epidermis, capable 

 of being partly detached but totally destitute of organi- 

 zation. 



The cortical glands, Saussure describes as being small and oblong 

 or circular bodies, encompassed by a fine thread or fibre s not imme- 

 diately attached to them, but separated by a narrow interval, and 

 communicating with the cortical net-work. Observ. sin- VEcorce dcs 

 Feuilles, Sfc. 



24. Mirbel will not allow the epidermis to be a dis- 

 tinct organ ; but supposes it to be the external layer of 



