ON THE CUTICLE OF PLANTS. 319 
walls of the cells of the epidermis, 'running without interrup- 
tion over their commissures, clothing the whole plant with 
the exception of the spongioles of the roots and most stigmas, 
but pierced at the stomata. In later treatises this membrane 
has received the name of cuticle. 
Treviranus (Physiol. I, 448) confirmed the existence of 
this outer membrane, though he did not regard it as a pe- 
culiar membrane, but considered it attributable to a conti- 
nued deposition of a coagulable substance from within or 
from without. 
I must myself plead guilty of another explanation of its 
origin, namely, from the expansion of the intercellular sub- 
Stance over the upper surface of the epidermal cells. I look 
upon this notion now as altogether erroneous, notwithstand- 
ing the support which it has received from Valentin (Reper- 
tor. für Anat. u. Physiol. 1. 100.) 
Link (phil. bot. edit. 2. I. 85) follows the view of Bron- 
Eniart, and says expressly that the cuticle can neither be 
regarded as the confluent outer walls of the epidermal cells, 
nor as a deposition of coagulable matter, relying on the 
distinctly defined separation between the cuticle and sub- 
jacent cells, as also upon the difference of colour in the parts 
exhibited by some plants. 
Meyen (Wiegm. Archiv. 1837. I. 221. Physiol. I. 176) ar- 
rived at a totally different result in his inquiries regarding 
the cuticle as nothing more than the incrassated outer wall of 
the epidermal cells. 
-Schleiden now opposes this explanation, and with Trevi- 
Tanus regards the cuticle as a mass secreted by the epidermal 
cells (Grundzüge d. Wiss. Botanik. I. 288.) He says that a 
gelatinous substance appears in the interstices between the 
individual cells which hardens and forms a network; at a 
later period the whole cell is covered with a similar layer, | 
Which unites with the network, and is quickly indurated ; 
then the epidermal cells secrete on their upper surfac p a 
less firm, and thick substance which raises up the earlier 
