THE ANGIOSPERMAE 



1421 



Three antipodals is by far the most general number, although they may 

 multiply secondarily. They are normally separated by delicate cell walls, 

 which, akhough at first plasmatic, later become 

 cellulosic. There are nevertheless a good number 

 of cases where cell wall formation does not occur 

 and the antipodal nuclei remain naked (Fig. 1312). 

 This has been observed in particular species, as a 

 more or less isolated phenomenon, in Cruciferae, 

 Melastomaceae, Polygalaceae, Liliaceae and Orchi- 

 daceae. It is generally associated with rapid 

 degeneration of the antipodals. 



A reduction in number below three is usually 

 associated with embryo sacs which are much nar- 

 rowed at the chalazal end and hence may be inter- 

 preted as due to restricted development. Individual 

 cases have been noted in Plumbaginaceae, Scroph- 

 ulariaceae and especially among the Compositae, 

 e.g., Helianthiis, Bidens, Arnica. 



Multicellular antipodal complexes are found in 

 families scattered through the whole of the system, e.g., Ranunculaceae 

 (Fig. 1313 B), Papaveraceae, Umbelliferae, Gentianaceae, Compositae, 

 Gramineae. In almost every case the condition is associated with excep- 

 tional development of the antipodals, either in respect of size, duration or 

 unusually large nuclei. So far as embryo sacs of the normal type are 

 concerned, it has been proved in many instances that the multiplication of 

 the antipodals is a secondary procedure and that it starts from the normal 



Fig. 1 3 12. — Thisniia anieri- 

 cana. Embryo sac with 

 free antipodal nuclei. 

 {After Pfeiffer.) 



Fig. 13 1 3. Unusual antipodal cells. A, Clematis sp. Two greatly enlarged 

 antipodals with chalazal extensions showing filiform apparatus like synergi- 

 dae. B, Trautvetteria polmata. Formation of a multicellular antipodal 

 tissue. (After Hiiss.) 



three. This makes it unlikely that a multicellular antipodal complex is a 

 primitive feature of the Angiosperms. 



