712 Mr. Brown on the Organs and Mode of 
This nucleus of the cell is not confined to Orchidez, but is 
equally manifest in many other Monocotyledonous families ; 
and I have even found it, hitherto however in very few cases, 
in the epidermis of Dicotyledonous plants; though in this 
primary division it may perhaps be said to exist in the early 
stages of development of the pollen. Among Monocotyledones 
the orders in which it is most remarkable are Liliaceze, Heme- 
rocallidez, Asphodelez, Irideze, and Commelinee. 
In some plants belonging to this last-mentioned family, espe- 
cially in Tradescantia virginica and several nearly related spe- 
cies, it is uncommonly distinct, not only in the epidermis and in 
the jointed hairs of the filaments*, but in the tissue of stigma, 
in 
* 'The jointed hair of the filament in this genus forms one of the most interesting 
microscopic objeets with which I am acquainted, and that in three different ways : 
lst. Its surface is marked with extremely fine longitudinal parallel equidistant lines 
or strie, whose intervals are equal from about 1-15,000th to 1-20,000th of an inch. 
It might therefore in some cases be conveniently employed as a micrometer. 
2ndly. The nucleus of the joint or cell is very distinct as well as regular in form, and 
by pressure is easily separated entire from the joint. It then appears to be exactly 
round, nearly lenticular, and its granular matter is either held together by a coagulated 
pulp not visíbly granular,—or, which may be considered equally probable, by an en- 
veloping membrane. The analogy of this nucleus to that existing in the various stages 
of development of the cells in which the grains of pollen are formed in me: same species, 
is sufficiently obvious. 
3rdly. In the joint when immersed in water, being at the same time freed from air, 
and consequently made more transparent, a circulation of very minute granular matter 
is visible to a lens magnifying from 300 to 400 times. This motion of the granular fluid 
is seldom in one uniform circle, but frequently in several apparently independent threads 
or currents: and these currents, though often exactly longitudinal and consequently in 
the direction of the striz of the membrane, are not unfrequently observed forming va- 
rious angles with these strie. The smallest of the threads or streamlets appear to 
consist of a single series of particles. The course of these currents seems often in some 
degree affected by the nucleus, towards or from which many of them occasionally tend 
or appear to proceed. They can hardly however be said to be impeded by the nucleus, 
for they are occasionally observed passing between its surface and that of the cell; a 
proof 
