1918] BUCHHOLZ—PINUS 197 
SUSPENSOR.—The tier of suspensor cells elongates and pushes 
the tier of embryonal cells into the cavity below. When the 
suspensor cells have elongated slightly more than in fig. 1, the 
embryonal cells give rise to the first embryonal tube initials (e:), 
and by the time the suspensor cells have elongated to the stage 
shown in figs. 39 and 40 another transverse wall has appeared in 
the apical cell below, giving rise to e,, the second embryonal tube 
initials. This is soon followed by the elongation of the first 
embryonal tube initials (fig. 6, ex) to form tubes like the suspensor 
cells, the first embryonal tubes. This added part of the suspensor 
is the secondary suspensor. 
Separation of the vertical rows of cells soon follows the division 
of the embryonal cells, although it may occur earlier, as is the 
case in fig. 37 at the left. In none of the species of pines studied 
was a single case found in which the 4 vertical rows of cells did 
not separate to form 4 embryos. It will be seen from a study of 
figs. 39, 40, 41, and 44 that the elongating first embryonal tubes 
are no longer in an even tier, and one of the embryos has already 
gained the lead in penetrating the endosperm. ‘The struggle for 
supremacy between the 4 primary embryos of an archegonium is 
well shown in figs. 40, 41, and 44, while in figs. 43 and 45 two arche- 
gonia are concerned. 
Since the primary embryos have now separated, we shall regard 
one of these 4 as the unit for discussion. One of the 4 suspensor 
cells and all of the cells formed below it by the embryonal cell 
constitute one primary embryo, while all the embryos produced 
by an egg will be spoken of as an embryo system. 
It is evident from a study of the development of the — 
part of the suspensor that the primary suspensor tubes never divide 
to form other tubes or cells. Likewise, an embryonal tube never 
undergoes division after it has begun to elongate, but an embryonal 
tube initial cell may divide by a vertical wall before elongation, 
"as eé, in figs. 6, 8, 14, and 20, or e, in figs. ro and 16. When the 
embryonal tube initial divides and gives rise to 2 or more cells 
in a tier, these elongate together into a collateral group of embryonal 
tubes (figs. 47-50), forming a suspensor division. ‘These suspensor 
divisions are all parts of the secondary suspensor, but when they 
