95 



Usually one sees that the pollentube, after having penetrated 

 into the embryosac begins to distend, a swelling which can attain 

 coUossal proportions (comp. fig. 40 PI. VI, fig. 41 PI. VII). This dis- 

 tension is probably due to a difference in concentration between 

 the cellsap of the pollentube and that of the embryosac, in 

 such a way that the former being more concentrated endosmose 

 sets in by which the turgor of the pollentube increases to 

 such an extent that the wall gives way before the strain and 

 bursts at the weakest place: the tip. After this has occurred 

 an open communication between pollentube and embryosac 

 content has been established, the two generative nuclei are 

 pushed into the embryosac while the vegetative or pollennucleus 

 usually, if not always, remains inside of the pollentube (comp. 

 f. i. fig. 41 PI. VII, fig. 36 PL VI, fig. 37, PI. VI, fig. 43, 

 42, 44 PI. VII, fig. 45 PI. VII etc.). 



COPULATION AND ITS PRODUCTS. 



At the moment the generative nuclei leave the pollentube 

 their appearance is like that pictured in fig. 41 PI. VII. The 

 chromatin is collected in more or less regular balls in the 

 center, accumulated in a mass which ressembles a raspberry 

 somewhat. 



A nucleolus can not be seen. The next stage I have obser- 

 ved is that pictured in fig. 42 and fig. 43. In both cases the 

 pollennucleus is seen lying inside of the pollentube, while be- 

 tween the nuclei of the fertil part of the embryosac two nuclei 

 of considerably larger size are seen. These are doubtless the 

 copulation products of the two generative nuclei with two 

 nuclei of the fertil part of the embryosac. 



The peculiar arrangement of the chromatin has disappeared 

 again, in fact the chromatin is not visible and each nucleus 

 is again provided with one or two nucleoli. These and the 

 following stages can best be seen by making a very thick 

 longitudinal section of the nucellus in such a way that the 

 embryosac is not injured; after that one isolates the embryosac 



