( 321) 
Hofmeister* in 1849 describes certain features of Cucur- 
bita, Stcyos, and Ecballium. He points out the fact that in 
these cases the embryo-sac before fertilization is very small 
compared with the size of the nucellus, that in each case it 
lies directly under the apex of the nucellus, which has a cen- 
tral row of cells with transparent contents. This condition 
probably led Amici to the view that the nucellus was tra- 
versed by a canal in its apical region. The main points 
which were contributed from Hofmeister’s researches may be 
summed up as follows: Shortly before the opening of the 
flower two nuclei appear at each end of the embryo-sac. 
Germinal nuclei arise from the micropylar cells with some 
exceptions (probably polar nuclei). The antipodals form no 
walls about themselves and their life is usually short. The 
odsphere is at first conical but later becomes elongated. The 
pollen-tube finds the micropyle while the flower is still fresh, 
penetrates the apex of the nucellus, and while surrounded 
with this tissue shows (upon treatment with potash) a wall 
transversely striated. The pollen-tube les against the 
embryo-sac and does not effect an entrance for about forty- 
eight hours, more or less. During this time the ovule retains 
its dimensions. Fertilization takes place suddenly, the em- 
bryo-sac increases from four to five times in length and twice 
in breadth. The odspore divides once transversely and the 
distal cell becomes the proembryo. The proembryo divides 
longitudinally forming two cells (Hcballium). A layer of 
free nuclei lines the embryo-sac and these form walls about 
themselves; a second layer is then formed, followed by a 
third, etc., until the embryo-sac is filled. It thickly surrounds 
the conical embryo, which must in turn replace it in its 
progress of development to the ripe seed. When the 
embryo is a conical mass of cells the endosperm occupies 
about one sixth of the space of the nucellus. Later stages 
show important features. Endosperm rapidly replaces the 
tissue of perisperm, especially about midway between micro- 
pyle and chalaza. The young embryo, from which the 
suspensor has already disappeared, soon shows radicle and 
