Endospermbildung bei Angiospermen. 533 



morphologischen Wert und auf die Endospermentwicklung einzu- 

 gehen. Die Spezialuntersuchung, die Sharp bei der Gattung 

 Physostegia vorgenommen hat, wäre wohl geeignet, Licht in 

 diese Sache zu bringen, dürfte jedoch in einem ' Punkt eine 

 ^ falsche Deutung einschließen. Der Embryosack von Physo- 

 stegia entwickelt hier noch vor dem jungen achtkernigen 

 Stadium von der Antipodenregion aus einen lateralen Zweig,' 

 der schnell in das Integumentgewebe eindringt und, da er 

 später fast das ganze Endosperm führen soll, den Endo- 

 spermlobus vorstellt. In jungen Stadien schreibt Sharp ihm 

 haustorielle Funktion zu. Für die Zeit der ersten Endosperm- 

 teilungen gibt der Autor folgende Schilderung der Vorgänge 

 im chalazalen Embryosackteil: »At about this time the anti- 

 podal cell which lies nearest the sac cavity takes on an 

 appearance quite different from the others. It becomes binucle- 

 ate, the cytoplasm changes in character, staining more 

 deeply and rapid enlargement causes its wall to become strongly 

 convex. This enlargement continues until the cell bulges out 

 conspicously into the embryosac cavity and its wall thus 

 partitions off the small pocket in which it lies with the 

 other antipodals. In stages somewhat later it bears much 

 resemblance to the first few cells of the endosperm, but the 

 possibility that it also is of endospermous origin is precluded 

 by the fact, that it has been observed side by side with 

 an undoubted endosperm nucleus resulting from the triple 

 fusion.« »The function of the cell in question is in all proba- 

 bility haustorial, recalling the behaviour of the basal antipodal 

 in several genera of the Galieae.« An einer anderen Stelle 

 sagt er weiter: »The formation of the endosperm is of consi- 

 derable interest. It is initiated by the division of the endo- 

 sperm nucleus, which occurs in the 'narrow region of the 

 sac, near the haustorial cell.« . . . The division is accom- 

 panied by a longitudinal wall running through the middle of 

 the sac. . . . Extension continues until it comes into contact 

 with the sac wall at or near the end of the endosperm lobe, 

 while in the micropylar lobe it was not observed to do so 

 an probably ends free.« »The cessation of endosperm forma- 

 tion at an indefinite point results in nuclei being left free in 



