Development, and Structure of the Vegetable Cell. 483 
It is this state of things which especially caught the attention 
of former observers, and which they represented as constituting 
the first indications of the special pollen-cells. 
Unger (Merismatische Zellenbildung bei der Entwickelung 
des Pollens, 1844) thus refers to the subject :—‘ At first some 
thin delicate striz make their appearance within the mother cell, 
which can, by making the cell revolve, be proved to be nothing 
else than transparent walls which divide the granular mass into 
several portions. They are so fragile that they dissolve in 
water.” 
These statements of Unger are entirely correct, supposing 
that the word “first” applies to the ready formed septa; but 
even in this condition the delicate membranes appeared to me 
in the end to_yield to the solvent energy of the water. 
And in fact, if we will not call in the aid of analogy in the 
interpretation of the phenomena, it seems impossible to prove 
that those free cells enveloped by the plasma within the pollen- 
mother cell and apparently soluble in water, and which may be 
recognized of different sizes within the unequally developed 
pollen mother cells of the same anther, form, by the mutual ap- 
- position of their enlarged membranes simultaneously with the 
assimilation of the plasma, the line-lke and exceedingly deli- 
cate septa (whose double nature can very rarely be detected), by 
which, in a subsequent stage of development, the turbid cell- 
juice of the pollen mother cell is subdivided. 
The conditions here prevailing do not allow, as in Gédogonium, 
of the actual and continuous observation of the growth of the free 
endogenous cells, the assimilation of the cell-juice enveloping 
them, and the formation and increase of their contents. Never- 
theless I consider that we are perfectly justified in inferring, 
from a certainly recognized fact, the occurrence of another 
similar one, although the latter cannot be observed with the 
same certainty; and I therefore assume that even the delicate 
septa, which at a certain stage of development divide the pollen 
mother cells, are the walls of those free cells which may be de- 
tected in them in other similar and earlier states. 
This opinion coincides with that of Mohl as expressed in his 
first-quoted essay on the development of spores. 
Moreover in spores, just as in pollen mother cells, four free 
cells are present, by the expansion of which so as to fully occupy 
the mother cell the septa in all probability originate. 
That these septa are not simple, as supposed by Unger (be- 
cause even in this very young state they cannot be split by the 
application of diosmotic fluids), but that they consist of two 
-membranes belonging to two approximated special mother cells 
of the pollen, was maintained even by Nageli, although he did not 
