92 
IOWA ACADEMY OF SCIENCES. 
( 22 ) Waugh, F. A. Pollination of the Plum. Bull. Vt. Agr. Ex. Sta. 
53: 47. 
( 23 ) Waugh, F. A. Pollination of Plums. Ann. Rept. Vt. Agr. Ex. Sti. 
12 : 189. 
( 24 ) Waugh, F. A. Pollination of Plums. Ann. Rept. Vt. Agr. Ex. Sta. 
11 : 238. 
( 26 ) Whitten, J. C. Studies in Plum Pollination. Rept. Mo. Hort. Soc. 
40 (1897): 101. 
( 26 ) Muller. Fertilization of Flowers. English Translation. Darcy W. 
Thompson. 222. 
( 27 ) Booth, N. O. A Study of Grape Pollen. Bull. Gen. N. Y. Agr. Ex. 
Sta. 224. 
( 28 ) Robertson, Chas. Flowers and Insects. Trans. St. Louis Acad. Sci. 
6:435. 
Fi'. 
a. 
Fig. 
b. 
Fig. 
c. 
Fig. 
d. 
Fi ?. 
e. 
Fig. 
f. 
Fig. 
g- 
Fig. 
h. 
Fig. 
i. 
Fig. 
j- 
Fig. 
k. 
Fig. 
1 . 
Fig. 
m. 
Fig. 
n. 
Fig. 
a. 
Fig. 
b. 
Fig. 
c. 
Fig. 
d. 
EXPLANATION OF PLATES. 
PLATE VI. 
A flower of plum showing stamens of two lengths, the shorter 
maturing first. 
A flower of a Japanese hybrid showing the stamens of two lengths, 
both maturing at the same time. 
A flower of the Wyant plum. 
A flower of Prunus domestica showing the slender pistil. 
A flower of the Wolf showing a perfect pistil. 
A flower of the Poole’s Pride, young flower just opened. 
A flower of the Wyant. 
A flower of the Poole’s Pride. 
A flower of the Surprise. 
A flower of the Wolf. 
A flower of the plum showing the method followed by the small 
bees in procuring nectar. These bees rarely affect pollination. 
Bee showing the pollen bags. 
Flower of the plum showing the method of the larger bees, such 
as the honey bees, when securing nectar. These forms are 
good pollinators. 
A flower of the Wolf showing an abortive pistil. 
PLATE VII. 
Embryo sac of the Wyant April 26. 17.5 long. 
An ovule of the Wyant showing the deeply placed Embryo sac. 
April 26. 
Embryo sac of the Wyant, May 5, 48 long. Egg nucleus, defini- 
tive nucleus and two synergids shown. 
Embryo sac of the Poole’s Pride, May 14. 525 long. Showing 
great development of the sac without increase in the number 
of the contained nuclei. Definitive nucleus and two synergids 
shown . 
