Researches into the Anatomy of Plants. 471 
spiral vessels, and at the other false trachee or porous 
tubes: the false partitions are formed in every kind of 
vessels. ; 
By a series of experiments I think I have ascertained that 
the spiral vessels gradually pass through all the other grada- 
tions of false trachew, &c. 
With respect to the obscure transverse lines or dark 
points in the false trachez or porous tubes, most botanists 
thought that they were caused by eminences (cowrrelets) 
distributed over the surface of the vessels, and which had 
a hole in the centre. The sassafras wood in fig. 7 seems 
to support this opinion; but I kave been convinced that it 
is erroneous by examination with the microscope. 
What is the function therefore of all these vessels ? 
They cannot be the sap vessels, for coloured liquids do not 
enter into them until they are cut, and form open capillary 
tubes. I have said that they were always empty. With 
their original discoverers, therefore, we must call them éra- 
chee, and [ think they contain the air necessary for the 
preparation of the sap. The analogy between plants and 
animals teaches us that this idea is correct, in the latter the 
bleed vessels are accompanied by receptacles for air. 
IV. VessELs pRopER, ReseRVOIRS OF THE Sap, AND 
Lacuna. 
The vessels proper are simple, straight, evlindrical, a 
little larger than the fibrous vessels, rarely solitary, being 
generally in bundles or fasciculi. They contain a milky 
white, green, yellow, red, or aqueous juice. They are 
easily known if they contain a coloured juice, but it 1s only 
by analogy that we can discover if they contain a green or 
aqueous juice. 
The following are the varieties : 
ist. The vessels proper in fasciculi run through the cellu- 
lar texture, the bark, and someiimes the pith; we find none 
in the wood. Asclepiades. 
ad. They accompany the fibrous vessels and the trachee 
in the stalk, but in the root they run through the bark. 
Euphorbiacez, Papaveracee, Umbelliferz. 
3d. They surround the fasciculi of wood dispersed in the 
stalk, but in the reot they adhere to the bark. Composite. 
4th. They form a layer almost without interruption 
under the bark of the stalk; in the root they follow the same 
direction. Ficus. 
All these organs merit the appellation of vessels, because 
they consist ef a proper membrane, but there are other 
Gg4 organs 
