1897 } THE POLLEN TUBE OF ZAMIA 455 
continuous. In most cases observed the spheres occupy positions 
on exactly opposite sides of the nucleus, but in a few instances 
they have been found much nearer together, being only about 
135° apart. The nuclei which these bodies accompany are at this 
stage in a resting condition, the contents presenting a fine gran- 
ular appearance and usually showing foam-structure more or less 
plainly. The nuclei are usually elliptical and about 80 » long 
by 56wide. The large nucleoli (20 to 24 w in diameter) con- 
tain numerous vacuoles. F requently several other small nucleoli 
may be observed in a nucleus. 
When the activity, which precedes fecundation, begins, the 
generative cell does not wander down to the distal end of the 
pollen tube as might be expected from analogy, but instead 
the proximal end of the tube (the pollen grain end) with the 
two cells, shown in fig. z, turns directly downward and grows 
through the apical tissue of the nucellus (fig. 6) and may be seen 
with a hand lens hanging down into the cavity formed above the 
archegonia. The pollen grain, constituting the extreme end of 
the now pendent proximal end of the tube, may be plainly seen, 
the two cells remaining in the same relation to the pollen grain 
as shown in fig. 7. All of the tubes examined show this same 
Structure, indicating that it must be the normal procedure. The 
first cell which protrudes from the old pollen grain remains in the 
Same condition, or in the most advanced stages yet studied shows 
_ indications of disintegration. The generative cell or second cell 
in the tube, which now lies above the first cell, has usuall y divided 
during this extension of the tube, or may be found in some stage 
of division. The two centrosome-like bodies which accompany 
_ ach generative cell and during the resting condition, as described 
_ above, occupied the poles of the nucleus corresponding to the ~ 
major axis of the cell and the longitudinal axis of the pollen tube, 
_ usually come to lie, during the migration of the cell into the now 
extended proximal end of the pollen tube, at two opposite points 
On the equator, the nucleus corresponding to the minor axis of ae 
| the cell or transversely i in the pollen tube. Whether this change ce 
in ual fasanige is —— ater by the eee * the centro 
