68 ON THE PLANT-CELL. 



thinks they originate from the union of rows of cells, but accurate ob- 

 servations do not support this view. Mirbel was the first to discover the 

 liber-cells.* Meyen, in his Physiology of Plants (vol. i. p. 107.), appro- 

 priates to himself their discovery, but does not say where his observations 

 on that subject are to be found. Mohl f first examined the liber-cells 

 with care. Upon the origin of the liber-cells Meyen has set forth a 

 peculiar view.J He believes them to originate in the union of rows of 

 parenchymatous cells. This view is founded upon erroneous observations 

 on the appearance of the liber-cells in the buds of dEsculus. 



28. H. FIBROUS TISSUE (Tela 68 



contexta) consists of very long, thin, 

 fibrilliform cells, intimately woven 

 and variously mixed with each other. 

 It is of two kinds. 



a. It exists in the Fungi as a soft, 

 almost sebaceous, and easily destruc- 

 tible cellular tissue. 



b. In Lichens as a dry, tender, 

 fibrous tissue, formed out of forked 

 and branched cells (fig. 68.). 



29. /. EPIDERMAL TISSUE ( Tela epidermoidea), is univer- 

 sally the most external layer of cells of a plant, so far as they can 

 be distinguished from the cells they cover, by their form and con- 

 tents. They only exist in the higher Cryptogamic and in nearly all 

 the Phanerogamic plants. 



It may be distinguished into, 



a. The Epidermis, a continuous layer of cells, which may be 

 again divided into three kinds, according to the medium in which 

 it is developed. 



1. Epithelium. Exceedingly delicate, homogeneous, transparent 

 cells, filled with colourless juices, and covering the surface without 

 forming intercellular passages. It is always present in the growing 

 parts of plants, and remains longest in closed cavities, as in the 

 ovary, but changes mostly into one or other of the following 

 forms : 



2. Epiblema, consisting of compact cells flattened outwards, though 

 not so at first, and without intercellular passages opening exter- 

 nally. They are developed in the water and in the earth. 



3. True Epidermis. It consists of very flat tabular cells, whose 

 walls laterally and outwardly are usually very compact. They are 

 generally placed close to each other; but in most plants there 



* Annales des Sciences Naturelles, 1835. 



f Erliiuterung meiner Ansicht iiber Structur der Pflanzcnsubstanz. Tubingen, 

 1836. 



| Wiegmann's Archiv, 1839. 



The English reader must not confound this with woody fibre, as this term has been 

 sometimes thus used by British botanists TRANS. 



68 Fibrous tissue from the inner portion of Cetraria islandica, from a section parallel 

 to its surface. 



