II4 BOTANICAL GAZETTE [FEBRUARY 
EXPLANATION OF PLATES IV AND V 
All figures have been drawn under Zeiss apochromatic objectives and 
compensating oculars with the aid of a camera lucida. Figs. 2-8 were drawn 
with 4 mm. obj. and compensating ocular 6; figs. 9-27, under obj. 3 mm. and 
ocular 12; figs. 28 and 29, under 3 mm. obj. and compensating ocular 6. 
Fig. 1.—Longitudinal section of a young cone from a terminal bud: s¢, 
ous lea Sp, set sporophyll; vb, vascular bundle; X12 
ial meristem of very young sporophyll drawn from same 
Spe a prea 
1G. 3.—Cross-section of a cone showing the sporangial meristems; X250. 
Fic. 4.—Longitudinal section of cone of same age as preceding: section 
passes through the stalk of the sporophyll and through the primordia of one 
sporangium in each row; c.ax, axis of cone; x2 ‘nt 
Fic. 5.—Transverse section of cone and long ction of sporangium: 
sporogenous tissue not defined; X 250. 
Fic. 6.—Same as fig. 5, but showing usual differentiation of sporogenous 
ae hase X 250 
G. 7. Vedat stage of differentiation of tapetum (4); X25 
oe 8.—Cross-section of sporangium after last eae division; 
X 250. 
Fic. 9.—Somewhat shrunken mother cell showing eight times increase in 
volume; X770 
Fic. ro. —Portion of a nucleus in which the heterotypic chromosomes are 
forming; le 
Fic. 11 the 8 heterotypic chromosomes; 770. 
Fics. 16 and 17.—Mature microspores; 770. 
Fic. 18.—Division of microspore nucleus; 770. 
Fic. 19.—Showing first prothallial cell the ee Sy io 
Fic. 20.—Mitosis of a prothallial cell; 770. 
Fic. 21.—Showing two tiers of prota (pe’ pe’’), primary sperma- 
togenous cell (.s.c.), and tube nucleus (#); 
Fic. 22.—Division of primary sone Aaa de cell; X770. 
Fics. 23-26.—Series of transverse sections of a pollen grain: pc’, basal tier 
of prothallial cells; pc’, second tier; im, tube nucleus; bcn, body cell nucleus; 
bc, body cell; sc, stalk cell; scn, stalk cell nucleus; 770. 
Fic. 27.—Shedding stage of pollen grain; 770. 
Fic. 28.—Body cell about October 15; 385. 
Fic. 29.—A male cell just before fertilization; 385. 
