102 MORPHOLOGY OF ANGIOSPERMS 



sue >s^ formed; (Fig, 41)*' . Tliis record indicates that the divisions 

 are variable in number even in the same species, and it may 

 be noted in this connection that while Schwere 42 states that 

 there are only three antipodals in Taraxacum, Hegelmaier 9 

 had previously reported four or five, and more than three have 

 been observed frequently in this laboratory. In many of these 

 cases all the cells usually contain two or more nuclei, and the 

 end cell toward the chalaza often becomes vesicular and multi- 

 nucleate, breaking through the sac and encroaching upon the 

 chalazal tissue. It seems to be clear that in the Compositae 

 this development of antipodals is practically an aggressive haus- 

 torium for the embryo-sac; while in the Ranunculaceae the 

 antipodals doubtless serve as an haustorium, but do not invade 

 the neighboring tissue. Certain Rubiaceae also contain active 

 antipodals, since Lloyd 67 lias found that in Vaillantia hispida 

 while two of the antipodals are insignificant, the third is very 

 prominent and remains active for a long time. The same au- 

 thor 105 has more recently found the same to be true of the 

 Galieae (Fig. 48), and he also has found four to ten antip- 

 odals in 'Diodia virginiana. Balicka-Iwano\vska 68 has also 

 noted enlarging and persistent antipodals in Plantaginaceae and 

 Campanulaceae, and their division in Dipsaceae as in the Com- 

 positae. In Asclepias, although three active antipodals are 

 usual, Frye 118 has observed compact antipodal tissue consisting 

 of seven or eight cells; and in A. Cornuti he has noted the 

 occurrence of tracheid-like cells at the base of the embryo-sac, 

 such as occur in Casuarina and Castanea. 



There seems to be no reason to question the ordinary view 

 that the antipodal cells are vegetative cells of the gametophyte. 

 Their polarity as contrasted with that of the egg-apparatus, 

 and their behavior when they function confirm it. The occa- 

 sion for their activity seems to be to supply the embryo-sac with 

 nutritive material absorbed from without at a time when the 

 endosperm has not been organized or other means of obtain- 

 ing nutrition are not available. In Monotropa uniflora Shi- 

 bata 122 has found that the three small antipodals disintegrate 

 after fertilization, but that when fertilization is prevented they 

 may enlarge enormously and fill a considerable portion of the 

 sac. The character of the active antipodals among the more 

 primitive Monocotyledons and in the Ranunculaceae may be 



