and Fertilization in Oenothera . 
295 
case to count the number of chromosomes has been observed. Once a 
nucleus in prophase of the second division was observed, in which 
fourteen chromatic filaments associated with two nucleoli were found 
(Text-fig. V, 9 ). This indicates the diploid nature of the endosperm 
nucleus. Renner (55) gave a good illustration of the nuclear plate found in 
the plasma sheet of the fertilized embryo sac in Oenothera biennis x Oe. 
Lamarckiana, in whichTourteen chromosomes are clearly delineated. This 
is the positive proof of a diploid nature of the endosperm nucleus. The first 
division of the fertilized egg nucleus occurs after several succeeding divisions 
of the primary endosperm nucleus ; for instance, the egg nucleus remains 
unchanged, while sixteen endosperm nuclei are found in the plasma sheet. 
An unusual case is shown in Text-fig. V, 10 ; in the upper right-hand 
side of the figure, a male nucleus ( m.n . x ) is shown just fusing with the egg 
nucleus ( 1 e.n .), and on the left-hand side the second nucleus ( m.n . 2 ) is shown 
lying beneath the chromatic plasma mass, while the third ( m.n. z ) is just 
coming into contact with the large pole nucleus (p.n). No shadow of the 
vegetative nucleus could be found in the sac, of course, so that those just 
mentioned above must be three sperm nuclei. For explanation of such 
an aberrant case two alternatives are proposed. The first is that the 
presence of excess nuclei is brought about by intrusion of two sets of sperm 
nuclei due to the attack of two pollen-tubes on a single embryo sac, though 
the fourth nucleus does not happen to be found in the preparation. The 
second is that it is due to the production of some excess generative 
nuclei in the male gametophyte. Among the Angiosperms visit of two or 
more pollen-tubes on a single embryo sac sometimes happens, as stated by 
Shattuck (61) in Ulmus americana, byjuel (34) in Saxifraga granidata, by 
Nemec (49) in Gagea lute a, by Compton (9) in Lychnis Flos-cnculi , by 
Weinzieher (74) in Xyris indica , by Nawaschin and Finn (48) in Juglans 
nigra and J. regia , by Tchernoyarow (70) in Myosurus minimus , and as 
described above in Oenothera (PI. VII, Fig. 8 ), although in the latter case it 
was often quite difficult to determine whether they represent both ends 
of a ramified tube or belong to different stocks. Unfortunately in the 
preparation containing the aberrant figure in question the pollen-tube 
is lacking, in consequence of an accident while preparing, so that the 
specimen was not complete enough to afford a decisive conclusion. Accord¬ 
ing to Weinzieher, two pollen-tubes pour out the contents into an embryo 
sac, but he does not mention anything about the further destiny of the 
poured contents. Nawaschin and Finn (48) report that two or three sets of 
male nuclei were often found ejected in a single embryo sac, but not two 
sperms fusing with an egg. The same was also observed by Tcherno- 
yarow (70). The latter three authors’ statements are illustrated by figures 
clearly delineated. Judging from the above-mentioned facts, especially the 
clear descriptions given by those three workers, it is reasonable to explain 
