126 BOTANICAL GAZETTE [ FEBRUARY 
The division of the nucleus of the pollen grain into a vegeta- 
tive and a generative nucleus, and the division of the latter into 
two sexual nuclei, apparently follows the usual order. The male 
cells are at first round, but in three of the five species examined 
they become greatly elongated, often acquiring a remarkably 
spermatozoid-like form. Such a form of male cells has been 
reported among various monocotyledons, but up to the present 
time Silphium is the only dicotyledon reported as showing 
them. 
The pollen tube enters the embryo sac just beyond the edge 
of the nucellar cap. Fertilization may be accomplished without 
the previous disorganization of either of the synergids. The 
division of the definitive nucleus precedes the division of the 
oospore. 
The first wall in the oospore is, as usual, transverse. It is 
possible, though not certain, that, unlike the other Compositae 
described, the terminal cell of the two-celled stage divides again 
transversely, and that the real ‘“ embryo cell” is the outer cell 
arising by this second division. 
The first wall in the embryo cell is a radial longitudinal one, 
instead of being transverse, as is said to be the rule for Com 
positae. The second or quadrant wall is likewise almost always 
longitudinal, and separates the two cotyledons. The transverse 
walls separating the octants are the third series to appear. 
The first series of walls in the outer octants is oblique, the 
dermatogen being cut off by the second series, In the inner 
octants the first walls differentiate the dermatogen, and the inner 
cells divide again to produce the periblem and plerome. 
The cell below the octants, cell c, by divisions exactly similar 
to those in the inner octants, forms a tier of cells which adds to 
all the primary tissues of the embryo. 
The periblem terminal is formed by the intersection of three 
oblique walls in the cell next below cell c. The other daughter 
cells in contact with the periblem, terminal complete the derma 
togen of the root, and by splitting form the first layer of the 
root cap. 
