SUPPLEMENTAL NOTE. 
531 
molecules, but the latter gradually become fluid, and vanish 
by absorption, till the cellules become completely clear and 
transparent. At this time, especially in the Spruce Fir, 
several embryo bags, generally from two to three, are dis- 
coverable ; they consist of a loose cuticle surrounding a gela- 
tinous kernel, which consists of large oblong cells, filled with 
matter, and lying among certain delicate branching threads, 
which have drops of some fluid sticking to their sides. The 
conjunction of the pollen tubes and the embryo bag continues 
for a long time after impregnation, in fact, until the embryo 
has acquired an oblong figure, and begins to grow lengthwise, 
becoming firm and nearly opaque. Soon after this all trace 
of the pollen tubes disappears." 
It therefore appears, 1st, That in Coniferaeat least, a direct 
communication takes place between the pollen tubes and the 
nucleus; 2d, That the pollen tubes not only touch the nucleus, 
but actually penetrate its substance to the very bottom (thus 
putting themselves in communication with the chalaza) ; 3d, 
That the origin of the embryo is owing to the discharge of the 
contents of the pollen tubes in the bottom of the nucleus ; and 
4th, That the embryo seems originally to grow at the expense 
of a peculiar matter contained in the cellular substance of 
the nucleus, which gradually becomes transparent as it is 
emptied by the absorption of the growing embryo. There 
are several other curious matters treated of in M. Corda's 
paper, which is extremely well worth the attention of phy- 
siologists. 
N N 4 
