PHYTOGENESIS. 253 
cell. A similar process occurs in the embryonal end of the 
pollen-tube, consequently in a highly elongated cell; I shall 
now proceed to describe the further development of the embryo. 
After the first cells, generally few in number, are formed, they 
rapidly expand to such an extent that they fill the pollen-tube, 
which soon ceases to be perceptible as the original enveloping 
membrane ; but at the same time several cytoblasts originate 
im the interior of each of these cells, and generate new cells, 
on the rapid expansion of which the parent-cells also cease to 
be visible and become absorbed. The same process is repeated 
indefinitely. But since the newly-generated cells have con- 
tinually less room to expand, and therefore constantly become 
smaller, the previous transparency is soon lost in consequence 
of the continual production of new cytoblasts in the interior, 
and the tissue becoming more and more compressed ; and from 
this stage to the perfect completion of the embryo we are con- 
ducted by the clearly logical inference that the process thus 
introduced continues the same, since no new force comes into 
operation which could induce us to assume a sudden variation 
of the vital action, more especially as we soon meet with the 
same manifestation of the vegetative power again. 
Meanwhile the seed germinates, and the embryo becomes a 
plant; and then indeed the question may arise,—Does the pro- 
cess of life continue the same thenceforward in the internodes 
and foliaceous organs? Now we are here very quickly con- 
vinced of the negative, that is, that a formation of new cells on 
the surface of the existing organs does not take place. The 
surface is always smooth, and generally covered in a very early 
state with a kind of epidermis, the outer layer being more 
transparent and almost as clear as water; and we never find 
even an indication of a newly-formed cell upon the surface. 
But if the embryo be the type of the entire plant, and the 
latter do not present anything which is not a repetition of its 
organs, if we have found the growth of the embryo to consist 
only in the formation of cells within cells, we may then expect 
to find the same result also in the process of the growth of the 
whole plant. It is especially a foliaceous organ, the anther, 
which has hitherto been studied and followed in its develop- 
ment by many celebrated men (particularly well by Mirbel) ; 
and here it is quite decided that the increase of cells takes 
