OF TIGRIDIA. 19 
pollen-tubes were long and very distinct (fig. 5, a, 6), some 
being filled with granules, others containing but few, and 
those near the end of the cells. 
At twenty-four hours after the application of the pollen- 
grains, the rest of the style and the ovary were examined. 
Pollen-tubes were found in both, and many of the ovules 
contained pollen-tubes in their micropyle-canals (fig. 6 e, 
Pies fig: 7,4, 0): 
2nd. Tigridia fertilised with the last. At the same hour 
in the evening all the style but one inch was removed. Ovary 
examined at the same time as the other, viz., twenty-four 
hours after the application of the pollen-grain, and multi- 
tudes of pollen-tubes were in the cells of the ovary and in 
the ovules. 
3rd. These experiments repeated, with same results. 
4th. Two inches of the style and stigma were removed four 
hours after fertilisation, and in the removed portion, the 
pollen-tubes were seen in abundance. 
5th. Dr. Maclean endeavoured in vain to prevent the 
plants seeding, by removing the style from the axis before 
the perianth had fallen. 
From these experiments it is proved that the impregnation 
is perfected in a little more than twenty-four hours; that the 
pollen-grain produces a tube-cell, which grows according to 
the manner of cells, which passes through stigma, style, and 
to the remotest ovule in the ovary—a space oftentimes of five 
inches—in twenty-four hours; that, taking the average length 
of the tissue to be perforated to be four inches, the pollen- 
tube grows at the rate of one inch in six hours; that before 
the pollen-tubes are half way down the style, if their con- 
nection with the pollen-grain be destroyed, they still grow and 
impregnate; that after the pollen-tube has fairly entered the 
style it is independent, both as regards its subsequent growth 
and impregnating properties, of the pollen-grain; and that 
the varying conditions of the atmosphere influence the ra- 
pidity of the growth of the pollen-tube, and consequently 
impregnation. 
Tearing the style with needles suffices to show the long 
pollen-tubes, and it is as well always to examine a non-impreg- 
nated style with the impregnated. No one can mistake the 
one for the other ; the abundance of very long cellular tubes, 
where all divisions are at right angles to the cell-walls, and 
which are to be traced several times across the field of the 
microscope, indicates the fertilised style. 
It is evident that a force of some kind is requisite to propel 
