AND ON POLYEMBRYONY IN THE HIGHER PLANTS, 3 
process in the fructification in Phanerogamia; that one, seldom 
several, of these tubes creep through the intercellular passages 
of the nucleus, and that the tube which reaches the embryo-sac, 
presses it forward, drives this before it, indents it, and then ap- 
pears like a cylindrical bag, forming the commencement of the 
embryo, which, therefore, is stated to be nothing more than a cell 
of the leaf-parenchyma ingrafted upon the summit of the axis. 
The embryo, according to this, therefore, is formed by the pollen- 
tube, and the indented embryo-sac; and in plants whose ovula 
contain several embryos, there would be just as many pollen- 
tubes present as embryos ; whence there is derived the important 
conclusion that the two sexes of plants have been named alto- 
gether erroneously, each pollen-grain being the germ of a new 
individual ; that the embryo-sac, on the contrary, should merely 
be considered as the male principle which only determines dyna- 
mically the organization of the material substratum. 
There are still, it is true, at the present time, many cases 
which might be mentioned, where, notwithstanding all care 
employed, no pollen-tubes have hitherto been detected during 
the act of impregnation ; but since, in by far the greater number 
of plants, the pollen-tubes are very easy to be observed on their 
‘way to impregnation, we may undoubtedly, with some jus- 
tice, presuppose this process of the fructification as being 
generally valid as regards the Phanerogamia. But, on the 
other hand, those observations of M. Schleiden are not correct 
according to which the embryo-sac is said to be common to all 
Phanerogamia. I have become acquainted with a large series 
of cases in which the embryo-sacs are wholly wanting; in the 
Monocotyledons this seems to be very generally the case, but 
there is no want of examples even among the Dicotyledons ; 
and recently MM. de Mirbel and Spach have proved the ab- 
sence of the embryo-sac in a number of Grasses*. In those 
cases, therefore, in which no embryo-sac exists, the formation 
of the embryo must there de seipso occur in another manner 
than according to that described in the new doctrine ; although, 
as we shall subsequently see, it is precisely these cases which 
apparently speak irrefutably in favour of M. Schleiden’s view, 
that the germ for the new individual is always contained in the 
pollen-grain, or in the pollen-tube. 
* Notes p.s.aVhistoire de VEmbryogénie Végétale. Par MM. Mirbel et 
Spach :—Compt. Rend. 1839, 18 Mars. 
B2 
