68 
ORGANOGRAPHY. 
BOOK I. 
same relation to the roots that buds bear to young branches. 
[Premier mem. sur les Lentic., in the Ann. des Sciences Na- 
turelles.) In Tree ferns it is hardly posssble to doubt that 
the tubercles so common on the surface of the trunk, are the 
points of roots either prepared for developement, or arrested 
in their growth by the dryness of the air that surrounds them ; 
for we find (in Dicksonia arborescens, for instance) that the 
part of the stem which is next the ground is covered with roots, 
and the part above it, surrounded by drier air, is covered 
with tubercles. But it is not at all improbable that the 
lenticular glands of the stems of ordinary trees, and the 
tubercles of tree ferns are different bodies, although con- 
founded under one name. 
It is extremely doubtful whether true lenticular glands are 
any thing more than portions of the epiphloeum, disorgan- 
ised by some unknown power. Mold states that they are 
found in the epiphloeum, that is, between the epidermis and 
the mesophloeum, and consist of greenish or colourless (or in 
Berberis yellow, and Sambucus red) cells which lie in rows 
perpendicular to the axis of the branch, and united towards 
the interior with the mesophloeum. He considers them a 
partial formation of cork.* Unger compares the true len- 
ticular glands to the Sorediae of Lichens, and the reproductive 
granulations of Jungermanniaceae ; and he considers them in 
some way connected with the respiratory process : even as 
obliterated respiratory organs. Meyen regards them, not as 
obliterated respiratory organs, but as formations intended to 
maintain an air communication between the exterior rind 
and the new green bark of trees ; for he says that the tissue 
of old bark is so compactly combined as to cut olf all direct 
communication between the air and the cavernous paren- 
chyma of the green bark. 
6. Of Prickles. 
Prickles [acidei) are rigid, opaque, conical processes, 
formed of masses of cellular tissue, and terminating in an 
* I take this from Taylor’s Magazine, xii. 58, where there is an (imper- 
fect ? ) translation of Meyen’s report on this and other subjects. Mohl’s 
original paper I have not seen, and the translation is in part unintelligible. 
