2(j REPORT ON BOTANY, MDCCCXLI : 
are different from the membrane formation. The spiral for- 
mation belongs to the membrane, because it is not dissolved 
by being boiled in caustic potass or soda. 
Mohl has taken great pains to refute Meyen’s assertion, 
that the vegetable membrane is formed of spiral fibres. This 
assertion is only of value as far as it goes, because, by far the 
greatest number of membranes, in the vegetable kingdom, do 
not exhibit such a composition. I told him, immediately, that 
I could not find what he had, even in the mrial roots of his 
Stelis. It is very remarkable, that many portions of plants 
have a tendency to split into a spiral line ; but this only takes 
place with the thicker parts ; for instance, with the old porous 
vessels, and even with the bark, as in the birch tree. We need 
not, therefore, go back with Mohl to a molecular position, 
but leave that to the natural philosophers. And if the mem- 
brane were ever so thin, it w^ould be a more simple assumption 
to suppose still thinner places, in which the membranes tear 
themselves to pieces. It is very true, that no definite and 
distinct difference exists between vessels and cells in the vege- 
table kingdom, yet we must retain the expression of the dif- 
ference for the science, in order to prevent confusion. If we 
were to call the external part of the flower of grasses, bracts, 
or leaves, because they, in point of fact, happen to be bracts, 
and eventually leaves, it would give rise to infinite confusion ; 
and how many terms would not be necessary, in order dis- 
tinctly to express what bract or what leaf is alluded to"? 
Raspail, indeed, has given such a description of grasses, and 
it was only owing to no notice being taken of it, that it did 
not occasion confusion. 
The vasa propria of the calyx of Chelidonium majus, I 
have caused to be represented in the second volume of the 
Icon. Sel. An. Bot., t. vi. fig. 1 (1840). The arrows attached 
to the figures indicate the direction of the current. It follows 
thence, that the current does not always originate in the flow- 
ing out of the juice from the parts that have been torn off, 
as many believe, and as, indeed, often is the case, for the 
stream by no means runs towards the outside, but rather from 
tlie outside towards the inside. As the calyx of Chelidonium 
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