1904 ] WYLIE; ELODEA CANADENSIS 15 
These enlargements vary in size from slight swellings to growths 
ten or fifteen times the normal diameter of the tube. Their con- 
tents were studied with interest, as it seemed they might throw 
light on the nuclear conditions in the pollen tube. Their stain- 
ing properties are uniform with those of the ordinary pollen tube, 
and nuclei are nearly always present, sometimes evidently disor- 
ganizing (fg. 73), but in other cases presenting a normal appear- _ 
ance. The tube nucleus was often quite conspicuous, but it was 
of special interest to note that in certain of these cystoids the 
male cells could be distinctly made out (figs. 70, 77, 72, 74). 
Each presented, under favorable conditions, its characteristic 
appearance. The ample cytoplasm was bounded by a definite 
membrane and showed within a distinct nucleus with its nucleo- 
lus. It was also noted that these male cells generally lie near 
one another, as though still joined together, and in certain cases 
this connection was very evident (figs. 70, 74). 
The presence of the male structures as distinct cells in these 
cystoids lying among the ovules affords very definite information 
as to their condition during the journey through the pollen tube, 
and it is obvious that they have retained the features that char- 
acterized them in the pollen grain. Guignard (6) has contended 
that the male structures are found as cells in the pollen tubes of 
Lilium, though this is denied by Koernicke (4). More recently 
Guignard (g) has reported a similar condition for Lepidium, 
which unfortunately is accompanied by no satisfactory figure. 
Since the tubes producing these cystoids in Elodea may be 
longer than the functioning ones, and apparently differ from 
them in no essential respect, it is probable that, in this form at 
least, the male structures regularly maintain their integrity as 
cells until they come into the vicinity of the micropyle. 
The pollen tubes of Elodea, furthermore, are remarkable for 
their persistence. Long after fertilization the enlarged tip of 
the pollen tube may be seen clearly outlined by the side of the 
suspensor cell (figs. 78-83), while stretching upward from the 
micropyle into the cavity of the ovary extends the tube still 
darkly staining and apparently turgid. These conditions persist 
until the embryo is well developed. Those portions of the tube 
