Tree (Ginkgo hi lob a, L). 
129 
/3. Male Flowers. 
The male flower 1 has the form of a catkin borne in the 
axil of a scale-leaf on a short shoot, with one or more bracts 
(Fig. 8, b) attached to the peduncle 2 . Usually two (Fig. 9), 
but not infrequently three, and more rarely four pollen-sacs 
(Fig. 7) depend from a slender filament terminating distally 
in a small knob, which appears as a broader fleshy disc, bearing 
four pollen-sacs in the stamen shown in Fig. 7. The pollen- 
sacs dehisce by a longitudinal slit on the inner side (Fig. 9). 
The wall of the sac consists of four to seven cells in breadth, 
and thickening bands occur on the walls of the outer layers. 
Thibout 3 has recently given an account of the structure of 
the pollen-sacs and filament; he suggests that the stamens 
with three pollen-sacs may point to the former existence of 
a type of Ginkgo stamen in which three was the normal 
number. The pollen-grains (30 \x x 10 \x) are characterized by 
a median depression along their major axis, and as Thibout 
points out they recall those of Cycads rather than the pollen- 
grains of Conifers 4 . 
The peduncle of the male flower adheres at its base to the 
subtending bract; in a section through the common base the 
vascular bundle of the peduncle is semicircular in form, and 
the two bundles of the bract complete the circle. In the free 
peduncle the xylem consists of nine or ten separate strands 
arranged in the form of an ellipse; there appears to be little 
or no centripetal xylem or transfusion tracheids. The fila¬ 
ment of a stamen is traversed by an axial bundle composed 
of about twelve tracheids radiating from a protoxylem strand 
(Fig. 50 ,px) ; two or three centripetal xylem-elements occur 
(cf. Fig. 50), also a few large transfusion-tracheids (to). 
At maturity—about the end of April—a pollen-grain con- 
1 Goebel (’81), p. 705 (PI. VI, Figs. 25 and 26 ), has described the development 
of the stamens of Ginkgo . 
2 Van Tieghem (’91). 3 Thibout (’96), p. 175 . 
4 Thibout (’96), p. 199 . Vide also Capellini and Solms (’92), PI. V; Wieland 
(’99), p. 389 . 
K 
