’ 
34 THe MIcRoscoPE, i 
glorious blossom. It is white, the filaments are white, as are the 
anthers, style and stigma. The whole blossom is like the ghost of a 
flower, shimmering white in the twilight. 
The plant is the Ipomeea Bona-now, L., a native of South Florida 
and of the West Indies. It seems to have been known for some . 
time as a green-house plant, and to have been extensively cultivated 
in the South, but it has only recently attracted attention as a 
desirable bloomer for out-of-doors during the summer and fall, at 
the North. Its botanical position is among the Convolvulacez. It 
is therefore related to the common “Morning-glory” of the gar- 
dens and fields. The five stamens shed so great a profusion of 
pollen that its abundance attracts attention, and it is to the structure 
of this pollen, with that of some of its allies, that I here wish to 
refer. 
Externally most pollen is beautiful, some being truly wonderful 
in its markings and appendages of projecting pores, spines, tuber- 
cles, or even lids that rise like circular valves to allow the fertilizing 
protoplasm to exude. It is the outer surface that the authorities 
say bears the markings and appendages, the grain being formed © 
of two membranes. The external coat, called the extine, is the last 
part of the grain to be formed within the anther. It is a secretion 
from the intine or internal membrane which directly envelopes the 
viscid, protoplasmic contents, the fertilizing material. The pollen 
tube which enters the stigma and passes down the style to the 
ovules, is produced by the growth and protrusion of this delicate 
internal membrane through the extine, this seeming to be its great 
function, if we exclude the more or less mechanical duty of envelop- 
ing the protoplasm. The extine adds another coat to the grain, thus 
increasing its firmness, and usually, always and exclusively, accord- 
ing to the authorities, bearing the markings that make pollen so 
attractive as a microscopic object. Gray says, that “‘to it all the 
markings belong ;’ and Balfour, in the Encyclopedia Britannica 
(the last edition ), that: “The extine is a firm membrane which 
defines the figure of the pollen grain and gives color to it. It is 
either smooth, or covered with numerous projections, granules, 
points, minute hairs, or crested reticulations. The intine is uniform 
in different kinds of pollen.” Other investigators make similar 
statements, descriptions that are true of most pollen. They are not 
quite correct, however, in connection with that of the “ moon-flower,” 
nor of some other members of the Convolvulacez. 
The pollen grains of the “ moon-flower” are spherical, white, and 
