POLLINATION OF THE MANGO. 9 
removed entirely. There was no appreciable difference between the 
covered and the uncovered sides of the tree in the number of fruits 
produced. 
THE POLLEN. 
SHAPE AND CHARACTERISTICS OF THE POLLEN GRAIN. 
In its normal dry state the pollen of all varieties examined exhibited 
an oblong-oval form, slightly broader hi some varieties and narrower 
in others, but approximating the same shape in all. When mois- 
tened by being placed in water the grains immediately swell and in 
a very few seconds have become spherical in outline, but on being 
allowed to dry out they resume their oblong-oval form. Under the 
microscope the dry pollen grains exhibit one or two sutures extending 
longitudinally; these disappear when the grain is moistened and 
swells. The thick outer membrane, or extine, is rugose on the sur- 
face and contains four pores, through one of which germination takes 
place. These pores frequently show very plainly after the pollen 
grains have been in a culture medium for 24 hours, the intine often 
protruding slightly from each of them. There are slight differences 
in the form of the ungerminated pollen grains of different varieties 
after they have been left for several hours in the culture medium; 
thus, it was noted that in some varieties the ungerminated grains 
commonly assumed a distinctly triangular outline, those of another 
variety were almost spherical, while those of still another were slightly 
oblate in form. 
NUMBER OF POLLEN GRAINS PRODUCED BY THE ANTHERS. 
The greatest variation was found hi the number of pollen grains 
produced by the anthers, not only among different varieties but in 
different anthers from the same tree. The smallest number was 
found in the anthers of the No. 11 seedlings examined at the Royal 
Palm Nurseries, Oneco, Fla. The trees were just coming into bloom 
after rather cold weather, and the flowers did not appear to be strong. 
The anthers were in many cases rather weakly developed and con- 
tained only 35 to 100 pollen grains, 200 being the largest number 
counted. Later in the season more than 400 grains were counted in 
anthers from other trees of this same race. The highest number 
counted was about 1,200, in the anthers of the Mullgoa (not Mulgoba), 
a variety in which staminate flowers greatly predominate and which 
produces more pollen than many others. An average number of 
pollen grains probably could be established for each variety and 
would be found to vary considerably in different varieties, some 
averaging not more than 400 or 500, while others certainly would go 
as high as 700 or 800. 
84444°— Bull. 542—17 2 
