Wenham, 071 the Vegetable Cell 
9 
moisture, from the infiltration of water into their cells. It is 
this same force which is chiefly instrumental in causing the 
distention of the detached vesicle or bag, of which each cell 
primarily consists, till at last contiguous walls become united 
throughout the structure. In some instances the force is not 
sufficient to cause the complete distention and union at the 
corners, consequently the leaf tissues of many plants are cha- 
racterized by little angular spaces, occupying the point of 
union between the confluent walls of neighbouring cells. 
It now remains to be asked, if the first origin of all parts of 
the vegetable structure consist merely of a protruding nodule 
of protoplasm, containing numerous cavities in size and posi- 
tion most irregular, what is it that determines whether this 
shall form either a stem, flower, or leaf at last, the first forma- 
tion being alike for each ? Tlie question is a difficult one to 
answer in all its details, but it may be stated with certainty 
that the primitive mass possesses no inherent power of its own, 
in either shape or substance, to arrange its destined form of 
growth. This is dependant entirely upon the influence of the 
adjoining, and more perfectly developed portions of the plant. 
In the case of a leaf, the soft cellular mass, while yet growing 
in the bud, is moulded to something like its proper form by 
the pressure of other leaflets, and when the cells of the embryo 
leaf have acquired some degree of consistency, a single spiral 
duct * is seen to grow out of the parent stem, forcing its way 
as an axis through the soft assemblage of cells. Others quickly 
follow, and lateral ramifications extend themselves as form 
requires. In the case of a leaf, all this may be very readily 
observed, but the formation of a flower-bud involves far more 
complicated conditions, with the whole details of which I do 
not profess to be acquainted. Fig. 12 will, however, serve as 
an illustration ; it is a group of embryo flowers, taken from 
the Arahis alhida^ during the month of October (the fully 
developed blossom not appearing until the ensuing spring) : 
<2 is a simple protuberance, filled with protoplasm, in its early 
stage of cell formation; Z> is a flower-bud, at a more ad- 
vanced period of growth, the centre being permeated by 
several spiral ducts and vessels. In the stages c, and e the 
ducts and vessels are still to be discerned, but very much in- 
creased in number and complexity ; f and g exhibit all the 
rudiments of the perfect flower, being apparently made up of 
* It has not been explained very clearly how these vessels are formed. 
By frequently observing their growing end among a mass of young cells, 
I have imagined that I have detected a disc-shaped cell at the extremity, 
by the successive formation and subsequent perforation of which the spiral 
duct is formed ; but the first growth is so indistinct and ill-defined, that 
I cannot at present affirm it with certainty. 
