584 ON THE USE OF POLLEN 
sesses an equal, if not a greater, physiological importance as 
the embryo. 
The importance of a character cannot, however, always be 
inferred from the physiological value of the organ. The con- 
sideration of the importance of the several modes becomes a 
chief element in this calculation. Now, the colour of the 
embryo is a character of very little value, being different in 
many allied species, and sometimes in the same individual. 
The number of grains of pollen contained in the anther-cell, 
is likewise an unimportant character, except in Asclepiadee, 
where, as I believe, and as I have elsewhere endeavoured to 
prove, the so-called pollen masses, are actually single grains. 
he figure of the pollen is of greater consequence, but still, 
not of so much as some writers have imagined. Thus, some 
genera of Proteacee have triangular, others oval pollen; in 
Fumaria the pollen is botryoidal, in Corydalis spherical; in 
Villarsia it is triangular, in Gentianella oval; in Ranunculus, 
Adonis, Anemone, etc. it is spherical ; ; In Delphinium, Aquile- 
gia, Aconitum, Helleborus, etc. it is elliptical; in Anchusa, 
Symphytum, Cynoglossum, Lithospermum, ete. it is panduri- 
form, or consisting of two equal spheres united together, and 
contained within a common membrane; in Borago it is 
spherical; while in Onosma echioides it consists of a larger 
sphere with a smaller one attached—a form evidently inter- 
mediate between the other two. In the nearly allied Helio- 
tropes, again, it is elliptical. Not only does the form some- 
times differ in neighbouring genera and species, but it is ob- 
served to vary, at different epochs, in the same plant. Thus, 
I have found the pollen of Ozalis, oval at the instant of plac- 
ing on the object-glass, almost immediately to become sphe- 
rical; and conversely, the pollen of Hippuris, spherical in 
the anther-cell, changes to a quadrangular outline upon 
removal. The same thing takes place in Rumex acetosa ; 
while in Polygala vulgaris, it is quadrangular in the anther- 
cells, but becomes rapidly round, upon exposure to air. The 
pollen-grains of Solanum and Atropa, under similar circum- 
stances, instantaneously change from spherical to elliptical. 
