126 
ORGANOGRAPHY. 
BOOK I. 
in the Lily, and several plants of the same family, the vesicles 
of parenchyma that are in contact with the lower cuticle are 
lengthened out, sinuous, and toothed, as it were, at the sides : 
these projections join those of the contiguous vesicle ; and a 
number of cavities is the consequence, which render this sort 
of parenchyma permeable to air. An analogous arrangement 
exists in the lower parenchyma of Galega. In the Iris, there 
is scarcely any space between the oblong and polyhedral vesi- 
cles which form the parenchyma ; but it is remarked, that the 
subjacent parenchyma is wanting at every point where the 
cuticle is pierced by a stomate. In such succulent plants as I 
have examined, the spaces between the cellules of parenchyma 
are very small ; but, nevertheless, here and there, there are 
often larger cavities, which either correspond directly with 
the stomates, or are in communication with them. The same 
thing happens in plants with floating 1 3aves, where the stomates 
placed on the upper surface correspond with the layer of the 
cylindrical and parallel vesicles ; in such case there are, here 
and there, between these vesicles, empty spaces which almost 
always correspond to the points where the stomates exist, and 
which permit the air to penetrate between the vesicles as far 
as the middle of the parenchyma of the leaf.” 
Thus much Adolphe Brongniart ; who adds, that in sub- 
mersed leaves there is no cuticle, but the whole consists of 
solid parenchyma alone, in which there are no other cavities 
than such as are necessary to float the leaves. The observ- 
ations of Mohl, Meyen, and myself generally confirm this ; 
but, at the same time, numerous cases exist in which the 
texture of the leaf has been found to be nearly the same 
throughout ; in fact, the only circumstance which is found to 
be uniform in respect to the internal anatomy of leaves is, that 
their parenchyma is cavernous, and that the air cavities are 
uniformly in communication with the stomates. 
Dutrochet states in addition i^Ann. des Sc., xxv. 245.) that 
the interior of a leaf is divided completely by a number of par- 
titions covered by the ribs and principal veins, so that the air 
cavities have not actually a free communication in every 
direction through the parenchyma; but are, to a certain 
extent, cut off* from each other. This is conformable to what 
