1918] BUCHHOLZ—PINUS 225 
embryonal tubes; ¢;,,third embryonal tubes; 0, portion of egg containing 
upper open tier of nuclei; 7, rosette cells; s, suspensor (primary suspensor) ; 
p, basal plate (plate of thickening usually formed above rosette); all figures of 
Pinus Banksiana unless otherwise indicated. 
IG. 1.—Section through base of archegonium, showing suspensor cells (s) 
elongating before lower tier of tip cells (a) found in 16-celled proembryo have 
ivided; ne corrosion cavity forming; June 20, 1914. 
IGS. 2-5.—Sections through 4 separated embryos all coming from the 
same egg, still even with each other, but with their apical ‘cell mitosis not 
simultaneous; mitosis shown results in second embryonal tube initial (e2) ; 
June 20, 1914 
1G. 6.—Vertical wall forming in second embryonal tube initial, which 
will result in a 2-celled suspensor division, as shown in fig. 8. 
1G. 7.—Later stage than fig. 6, in which an oblique wall has been formed 
by apical cell and no-vertical wall has yet appeared in any embryonal tube 
initials, 
Fic. 8.—Later stage than fig. 6, in which a 2-celled suspensor division has 
begun to elongate; first oblique wall cut off by apical cell has just been formed; 
June 30, 1916. 
Fic. 9.—Later stage, in which first oblique wall of apical cell is only 
slightly ‘tilted; 2-celled embryonal tube division has become well elongated; 
July 1, 1916. 
Fro, 10.—Apical cell of Pinus Laricio, forming first oblique wall, in this 
case almost vertical; July 6, 1916. 
Fics. 11, 12.—Usual appearance of embryos with first oblique wall formed 
by apical cell; June 29, 1916. 
Fics. 13, 14.—Occasional appearance of embryo after vertical wall has 
been formed by division as shown in fig. 10; in fig. 14 embryonal tube initials 
(upper cells of group) have ae leaving only 4 cells below; fig. 13, June 
22, 1914; fig. 14, July 1, 1916. 
Fic. 15.—Pinus Laricio, showing how second fet wall is formed by 
apical cell after first has appeared vertical; July 16 
Fic. 16.—Usual condition after first 2 obliqut oe have been formed; 
July 1, 1916. 
Fic. 17.—Later stage with A mere cell placed slightly to one side; 
apical cell has 3 cutting faces; Jun 
IG. 18.—Usual condition of slightly older embryo; June 29, 1916. 
Fics. 19, 20.—Embryos with apical cell in rather unusual position; 
June 30, 1916. 
IG. 21.—Two views of same embryo; a, in a high plane of focus, showing 
shadows of lower nuclei; }, showing only nuclei of lower plane of focus and 
walls; apical cell difficult to distinguish with certainty; June 22, 1914. 
Fics. 22, 23.—Older stages than last, with distinct apical cells; July 5, 
1916. 
