146 Agnes Robertson. 
division which is found in different years on days so far apart as 
June 1st and June 24th. The mother-cell divides into four, of 
which the basal cell is the embryo sac. Starch is present when 
the mother-cell first becomes distinguishable from its neighbours, 
and it has not disappeared when the division into four is completed. 
EXPLANATION OF PLATES III. AND IV. 
Illustrating Miss Agnes Robertson’s Paper on “ Spore-Formation 
in TORREYA CALIFORNICA.” 
Plate III.— The Staminate Cone. 
Fi‘*. 1. Staminate Cone in winter resting condition enclosed in its bracts 
(x 2) (see Fig. 8.) Collected November 10th, 1902. 
Fig. 2. Staminate cone collected March 19th, 1902, shewing bracts beginning 
to open, (x 2) (cf. Fig. 9.) 
Fig. 3. Staminate cone collected April 8th, 1902 (x 2). (See F'ig. 10). 
Fig. 4a. Ripe staminate cone collected May 31st, 1902 (x 2.) The sporophylls 
are now fully exposed. At this stage the pollen grains are 
bi-nucleate. (cf. Fig. 12c.) 
F'ig. 4b and 4c. Enlarged dorsal and ventral view of a single sporophyll with 
four pollen sacs from the cone drawn in Fig. 4a. 
Fig. 5a. Dr}- cone which lias has shed its pollen grains (x 2). Collected 
June 1st, 1904. 
Figs. 5b and 5c. Enlarged dorsal and ventral view of a single sporophyll 
from the cone drawn in Fig. 5a. The pollen sacs have opened by 
slits on their lower sides, and the whole sporophyll and the sacs have 
shrunk considerably. 
Figs. 6a —6h. Diagrams of the tips of eight cones collected on May 31st, 
1902 (see Fig. 4a) viewed from above, shewing the different arrange¬ 
ments of the sporophylls at the cone apex. 
Fig. 7a. Longitudinal (nearly radial) section of a young stamen (x 21). Cone 
collected March 4th, 1902. (r, resin duct,; t, tapetum ; p, pollen 
sac. 
Fig. 7b. Transverse section (tangential to the whole cone) of a young stamen 
( x 21). cone collected March 4, 1902. Lettering as in F'ig. 7a. 
Fig. 8. Pollen mother-cells in winter resting condition (x 600). Collected 
November 10th, 1902. (c.f. F'ig. 1). 
Fig. 9. Pollen mother-cells in synapsis (x600). Material collected March 
19th, 1902, (c.f. Fig. 2). 
Figs. 10a — 10g. Tetrad division of the pollen mother-cells (x600). Mate¬ 
rial collected April 8th, 1902 (c f. F'ig. 3). 
l-igs. 10a and 10b. Pollen mother-cells shortly after the reduction division. 
F'ig. 10c. Three chromosomes from a polar view of one of the two daughter 
nuclei resulting from the reduction division. 
Fig. lOd. Second division occurring in a pollen mother-cell before the two first 
two daughter nuclei are separated by a wall. Note the contrast 
between their chromosomes and those shown in Fig. 10c. 
Fig. lOe. Four daughter nuclei formed, but mother-cell still only divided into 
two. In this case, as in F'ig. lOd, the four daughter nuclei lie in one 
plane. 
Figs. lOf and lOg. Cases of tetrad formation. 
