Bauhaus-Universität Weimar

Microscopical researches into the accordance in the structure and growth of animals and plants
Schwann, Theodor Schleyden
margin of the cytoblast, and quickly becomes so large that the 
latter at last merely appears as a small body enclosed in one 
of the side walls. At the same time the young cell frequently 
exhibits highly irregular protrusions (fig. 1, c), a proof that 
the expansion by no means proceeds uniformly from one point. 
During the progressive growth of the cell, and evidently arising 
from the pressure of the neighbouring objects, the form be¬ 
comes more regular, and then also frequently passes into that 
of the rhomboidal dodecahedron, so beautifully defined à priori 
by Kieser. (Compare fig. 1, from b to e, with fig. 8.) The 
cytoblast is still always found enclosed in the cell-wall, in 
which situation it passes through the entire vital process of the 
cell which it has formed, if it be not, as is the case in cells 
which are destined to higher development, absorbed either in 
its original place, or after having been cast off as a useless 
member, and dissolved in the cavity of the cell. So far as I 
could observe, it is only after its absorption that the formation 
of secondary deposits commences upon the inner surface of 
the cell-wall (fig. 9). 
As a general rule, it is rarely that the cytoblast accom¬ 
panies the cell which it formed through its entire vital process ; 
nevertheless, it is, 
1. Characteristic of the families of the Orchideæ and Cacteæ, 
that in them a portion of their cellular tissue remains in a 
lower stage of development during the entire period of life. 
2. In various plants it occurs that cellular tissue, which has 
merely a transitory signification, is not perfectly developed, 
but retains the cytoblast, and is absorbed together with it at a 
subsequent period. Yet I have also remarked that the latter 
in the middle period of its existence lost much of its distinct¬ 
ness and sharpness of outline, which, however, reappeared when 
absorption commenced; for example, in the nucleus of the 
ovule of Abies ex cels a, Tulipa sylvestris, and Daphne alpina. It 
is most extraordinary that some physiologists should have felt 
prepared to deny the fact, that absorption takes place in plants, 
since even very considerable portions of cellular tissue of the 
nucleus of the ovule, for instance, become completely fluid 
again, and are received into the common mass of the sap. It 
is true this only takes place so long as the cell still consists 
of the simple original membrane, and is not so far advanced


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