36 ‘SPERMATOGENESIS AND. FECUNDATION OF ZAMTA. 
ently did not observe the process of division leading to the formation 
of the second nucleus, and Strasburger was unable to confirm this por- 
tion of Juranyi’s observation.' Recently, however, several investi 
gators have found the pollen-tube nucleus in various other plants to 
divide, at least occasionally. This was first observed by Chamberlain 
in Lilium philadelphicum (19), and later by Fullmer (42) in Hemero- 
callis fulva. A somewhat careful search was therefore made in various 
stages of developing pollen tubes of Zama for a division of the pollen- 
tube nucleus, but no indication of such a division has ever been 
observed. Furthermore, in an examination of the tubes where the 
nucleus is found near the central cell no case has been found where a 
second nucleus occurs at the apex of the tube. It would thus seem 
that the tube nucleus remains at the apex of the tube as long as this 
is the end where the most active growth is taking place, and then, 
when the active growth begins at the base of the tube in its elongation 
preceding fecundation, it migrates to that end of the tube in order to 
be near the point of greatest activity and superintend the growth of 
the pollen-tube wall in this location. Haberland (50), in his extensive 
paper on the relationship between the function and position of the cell 
nucleus in plants, has shown that the nucleus ordinarily takes position 
in the cell near the point of most active growth. The writer has come 
to the conclusion that in Zama the pollen-tube nucleus remains nor- 
mally near the distal end of the tube as long as the tube is growing in 
length and absorbing nutrition. The growth of the basal end of the 
tube does not start, apparently, until the tube has attained its full 
development in length in the apical portion. The tube nucleus then 
migrates to the base of the tube, the increased length of that end of 
the tube being due to the growth of the pollen tube in that region, 
thus necessitating the presence of the nucleus. This migration of the 
pollen-tube nucleus was not discovered until the writer was closing 
his investigations, and has not been as thoroughly investigated as 
the other processes of development described. He feels, however, 
that there is but little doubt of the correctness of the interpretation. 
Since this conclusion was reached the writer finds that the same migra- 
tion of the tube nucleus was observed by Ikeno (69, p. 573). 
In the middle of September the embryonal nucleus [tube nucleus] begins to move 
forward toward the body cell (fig. 22a, Pl. IX), and by the end of the same month 
it comes in contact with its posterior end, so that at this time the body cell and the 
outer prothallial cell, as well as the embryo-cell and stalk-cell nuclei, meet at the 
terminating exine end of the pollen tube.? 
| Ebensowenig trat uber gepriiften Falle der Pollenschlauchkern auch nur ein ein- 
ziges Mal in Theilung ein. (Strasburger, 109, p. 3.) 
2Mitte September beginnt der Embryonalzellkern [tube nucleus] nach der Kor- 
perzelle sich hinzubewegen (fig. 22a, Taf. IX) und Ende desselben Monats kommt er 
in Contact mit ihrem hinteren Ende, so dass zu dieser Zeit sowohl die Korperzelle 
und die iiussere Prothalliumzelle, als auch der Embryonalzell- und der Stielzellkern 
an dem mit der Exine abschliessenden Ende des Pollenschlauches zusammentreffen, 
