INTERNAL STRUCTURE OF PLANTS. 
27 
is very thin, we only need to tear off the small leaf, with- 
out making any incision, when it leaves only a small spot from 
wliich the juice can flow. This discovery, made by Herr 
Schultz, is therefore certainly a peculiar discovery, and is 
readily seen, without there being any necessity for making the 
observation in sunshine. For the movement which is seen in 
the sunshine, especially in leaves that have been torn off, is an 
optical delusion, and the stream may be directed at pleasure 
towards one or towards the other side, according as one turns 
the mirror. Professor Amici convinced me of this, at the 
Assembly of Naturalists at Pisa, in the autumn of 1839. The 
flickering motion, which is seen simultaneously with this, may 
likewise be owing to an optical delusion. These peculiar 
vessels, which in Latin one might probably term vasa latici- 
fera^ are by no means always simple in Chelidonmm majus, as 
I formerly believed, but branched. Simple they certainly are 
in the vicinity of the leaf nerves, and in that of the bark of the 
root, and in the wood of the trunk. As such they have also 
been represented in the Icon. An. Bot. tab. 14, figs, 6, 7, 8. 
It appears to me, that the branching of these vessels may be 
mentioned as a principal character, by which they may be 
distinguished from all other vessels, even when they have no 
coloured juice. But these vessels must not be mistaken for 
the long cells, or the vessels in the accompanying tissue (the 
woody bundles), which never are branched, never carry a 
coloured juice, and in Avhich a movement of juice has never 
been observed, which mistake, indeed, has been committed by 
many, and is still made. The circumstance of the latex vessels 
having been investigated only in the vicinity of the woody 
bundles of the trunk, and of the leaf nerves, in which very 
localities they are simple and similar to those of the liber, has 
given rise to this error. Their curved and branched forms may 
soon, however, be found, when they are examined in the flat 
parts, and removed from the nerves, 
Stomata are represented in the second volume of the Icon. 
Sel. F, 2 (1840), tab. 4 and 5. First, Stomata of the usual 
form, consisting of two curved cells, having a slit-like opening 
between them, and which are surrounded by one or more 
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