Spore Formation in Torreya californica. 
147 
Fig. 11. Section of d part of a pollen sac from a staminate cone 
gathered April 22nd, 1904 and kept in water until April28th (x 600) 
w, wall layer; t, tapetum. The pollen-grains are still grouped in 
tetrads, double tetrads, or pairs. Occasional traces of the walls of 
the mother-cells are seen. 
Figs. 12a—12e. Different stages in the division which separates the generative 
nucleus from the tube nucleus, (x 600). Material collected May 
17th, 1904. 
Fig. 12a. Resting nucleus. 
Fig. 12b. Nucleus in spirem. 
Fig. 12c. Obliquely cut spindle. 
Fig. 12d. Two similar daughter nuclei still united by threads. 
Fig. 12e. Differentiation of the two nuclei (tube nucleus and generative 
nucleus) e, exine ; i, intine. 
Fig. 13. Ripe pollen-grain examined dry, shewing triradiate ribbing, (x 600). 
Material collected May 17th, 1904. 
Fig. 14. Ripe pollen-grain examined in aqueous iodine, (x 600). e, cast off 
exine ; i, swollen intine. 
Fig. 15a and 15b. Transverse and tangential views of the wall of a ripe pollen 
sac to shew ribbing of outer layer of wall, (x 140). Material 
collected May 17th, 1904. 
Plate IV.— The Ovules. 
Lettering throughout :— n, nucellus ; i, integument; l, leaf subtending 
ovules; B and B ', bracts in whose axils flowers arise ; b and b 2 , lower pair of 
bracts at base of ovule; b 3 and b 4 , upper pair of bracts at base of ovule; 
r, resin passage ; a, arillus ; e.m.c, embryo-sac mother-cell. 
Fig. 16. Longitudinal section (radial to the fertile shoot) of an ovule from a 
winter bud. (x 21). Collected December 1st, 1902. 
Fig. 17a. Longitudinal section (radial to the fertile shoot) of an ovule 
collected March 4th, 1902. (x 21). 
Fig. 17b. 
Fig. IS. 
Fig. 19. 
Fig. 20a. 
Fig. 20b. 
Fig. 21a. 
Fig. 21b. 
Fig. 21c. 
Transverse section of a pair of ovules collected on the same date as 
that drawn in Fig. 17a. (x 21). 
Longitudinal section (tangential to the pair of ovules) of an ovule 
collected March 19th, 1902. (x 21). 
Transverse section of a pair of ovules collected April 8th, 1902. 
(x 21). 
Transverse section of a single ovule with its bracts collected April 
28th, 1902. (x 21). 
Longitudinal section of a single ovule without its bracts, collected 
on the same day as that drawn in Fig. 20a. ( x 21). 
Fertile terminal bud which would develope into a leafy shoot in the 
current year, surrounded by four of last year’s leaves. Collected 
May 8th, 1902. (Nat. size). 
Pair of ovules with subtending leaf from the fertile bud drawn in 
Fig. 21a. (Nat. size). 
Longitudinal section (tangential to the fertile shoot) of a pair of 
ovules such as that shewn in Fig. 21b. (x 21). Collected May 8th, 
1902. The position of the growing point, which does not shew in 
the plane of this section, is indicated by a dotted line between the 
ovules. 
Fig. 22a. Pair of ovules with subtending leaf, collected May 21st, 1902. 
(Nat. size). 
Fig. 22b. Longitudinal section of a single ovule collected May 21st, 1902. 
(X 21). 
