62 
Wenham, on the Vegetable Cell. 
cells ; for, though they are most useful for testing the transi- 
tion stages between protoplasm, starch, and cellulose-layers, 
&c., they are extremely prone to develop an appearance of 
membranes and organisms that do not really exist. I much 
prefer, when the case will admit of it, to view the structure 
and note the successive stages of development under natural 
conditions. I am, however, far from wishing to disparage the 
valuable test referred to. The effect of sulphuric acid and 
solution of iodine, in the young cells in the cases in question, 
is to cause the cavities in the formative plasma to become 
more distinctly apparent, as perfectly clear spaces, containing 
nothing else but a watery fluid. The objection that I have 
sometimes found in using it is, that in the boundary of a 
consolidated plasma, known to be homogeneous, it is apt to 
develop the appearance of layers, or zones, not arising from 
cellulose deposits, but caused by the grades of chemical 
action of the test. When young cells contain but a small 
quantity of contents, another fallacy may arise, from the 
application, for they become drawn together in the centre of 
the cavity, appearing as a ball of nucleus. 
As a further explanation, which must be considered supple- 
mentary to my former paper, I have now some additional 
remarks to make on vegetable cell development. 
The basis of a cellular structure in its first stage, — consist- 
ing of a membranous sac filled with an uniform plasma, or 
mass of formative material, — may be termed by some, " the 
primordial cell ;" but in my view improperly, for the external 
membrane is merely protective, it exerts no active influence 
upon, and is unconnected with the subdivision, or cellulation 
of the contents, and, taken as a whole, has none of the func- 
tions of an individual cell.* 
Now we have here a vesicle filled with formative material, 
ready to break up into a group of cells. Those who have 
examined for themselves with the requisite degree of care 
must recognize a simultaneous development, numerous rudi- 
* When the cuticular envelope, containing the uniform plasma, is 
ruptured under water, the protoplasm sometimes escapes as a globule, 
which speedily becomes filled with vacuoles. These rapidly enlarge and 
increase in number, till the whole becomes spread out and diffused in the 
fluid. The tunic, or envelope of young cells, does not at first, in all cases, 
possess an uniformity of surface ; for, in many plants it is spinous, or 
covered with tubercules, at its earliest stage ; these are the rudiments of 
hairs. Jt is remarkable at what an early period they are perfectly deve- 
loped, even before a definite or complete cellulation of the plasma, that 
they have sprung from, has taken place ; some of the hairs being already 
jointed, and showing sap-currents in their cells. 
t When the bark is strij)ped from the growing branches of exogenous 
plants, early in the spring, the surface of the wood is covered with a slimy 
