A 
BEHAVIOR OF THE POLLEN TUBE 99 
dermis, and, as above said, coalescing with its outer wall. It is not 
clear, however, whether the pollen tube wall as represented, and 
as it appears to the eye in the preparation belongs, properly 
speaking, entirely to the pollen tube. At any rate the soft char- 
acter of the walls and their coalescence makes the determination of 
this point difficult. 
When the pollen tube reaches the 
lower end of the strophiole, it travels, as 
before, superficially around and into the 
rift between this and the integument. This 
rift is filled with the slimy secretion de- 
rived entirely from the epidermis of the 
strophiole, inasmuch as the epidermis of 
the integument is not secretory. In this 
way the micropyle is at last reached and 
entered. 
If now we compare the three types de- 
scribed as regards the development of the 
strophiolar conductive tissue, and the be- 
havior of the pollen tube, we may accord- 
ingly arrange them into a series in the 
following order and with the characters 
indicated. Fic. 11. Diodia Virgini- 
I. Diodia Virginiana.—The conduct- ana. Ovule and portion of the 
ive tissue consists of epidermal cubical wes E HA peia ase 
cells with thickened outer walls covered ” ^ ° 
with a mucilage secreted by them. The mechanical relations of the 
ovary are'such that the pollen tubes may easily lie between the 
strophiole and the ovary wall. The pollen tube travels super- 
ficially along the funiculus and strophiolar conductive tissue, but 
imbedded in the mucilaginous secretion. 
2. Diodia teres.—The conductive tissues consists of columnar 
epithelial cells with thickened outer and lateral walls. The middle 
lamella is mucilaginous. There is no'secretion on the outer sur- 
face. The mechanical relations are such that the strophiolar con- 
ductive tissue is compressed between the ovule and ovary wall. 
The pollen tube enters the said conductive tissue immediately on 
commencing its upward movement along the funicle and remains 
within till it reaches the micropyle. * 
