446 BOTANICAL GAZETTE [December 



micropylar and the chalazal haustoria, the latter are the larger. 

 As there are no nutritive tissues at the micropylar end of the sac, 

 this accounts for the micropylar haustoria being less developed than 

 those of the chalazal end of the embryo sac. The chalazal haustoria 

 also have a greater region of nutritive tissue from which to absorb. 

 The haustoria attain their greatest development when the endo- 

 sperm is being formed most rapidly. As the embryo reaches 

 maturity only traces of the haustoria remain. 



In the Rhinantheae and other members of the Scrophulariaceae 

 micropylar and chalazal haustoria appear to be quite constant 

 characteristics. The form of the haustoria and the extent to which 

 they are developed vary considerably among the different species, 

 for in Melampyrum memorosum they are very arborescent, while 

 in some of the other species only rudimentary haustoria appear. 

 In Scoparia no haustoria are noticeable. Balicka-Iwanowski 

 is inclined to think that the micropylar haustoria are not trans- 

 formed synergids, while Schlotterbeck, to whom reference is 

 made, takes the opposite view. The writer interprets the micropy- 

 lar and the chalazal haustoria as transformed endosperm cells. 



Endosperm 



The secondary endosperm nucleus migrates to the lower central 

 part of the embryo sac, and endosperm formation begins with the 

 division of the endosperm nucleus. The secondary endosperm 

 nucleus divides transversely to form the nuclei, and almost imme- 

 diately a cell wall is formed between them. Each of the two endo- 

 sperm cells now formed divides longitudinally, and thus four cells 

 are formed. At this stage (fig. 24) the egg and the two synergids 

 were still observed at the micropylar end. The lower two of the 

 above four cells form the haustoria, while the upper two divide 

 transversely and then longitudinally to form eight endosperm cells 

 (fig. 25). At this stage four haustoria are observed at the micropy- 

 lar end of the embryo sac. They are put out as prolongations of the 

 four micropylar endosperm cells. One cannot regard the micropylar 

 haustoria as transformed synergids. Rapid nuclear division now 

 ensues without reference to these rows of endosperm cells. Endo- 

 sperm formation takes place before the first division of the egg. As 

 the embryo matures, the surrounding endosperm storage cells 



