THE FEMALE GAMETOPHYTE 



101 



of Casuarina, but in this latter 

 instance thev are derived from 

 mother-cells. Other Arehichlam- 

 ydeae with active antipodals are 



Heckeria (Johnson 114 ), in which 

 they are sometimes six to eight in 

 number; Asarum (Hofmeister 2 ), 

 in which thev are very lono-, ex- 

 tending at fertilization from one- 

 ihird to one-half the length of the 

 embryo-sac, and sometimes divi- 

 ding; Jefferson ia diphylla (An- 

 drews 37 ), in which they become 

 about one-half as long as the 

 embryo-sac ; Eriobotrya ( Guig- 

 nard 12 ), in which they are large; 

 and Anoda (Guignard 12 ), in 

 which they are prominent and 

 often binucleate. 



Among the Sympetalae the 

 Compositae are especially note- 

 worthy for the extensive develop- 

 ment of the antipodal region (Fig. 

 47). In this familv the chalazal 

 end of the elongated sac is very 

 narrow and the antipodals are 

 superposed. In a number of 

 eases, as in Doronicum, Petasites, 

 and Taraxacum, there are usually 

 only three antipodals, but they 

 remain active ; while in Tussila- 

 c]o (Guignard 12 ) there are usual- 

 ly four: in Senecio (Alottier 29 ) 

 two to six; in Silphium (Aler- 

 rell 77 ) three to eight; in Conyza 

 'Guignard 12 ) eight to ten; in 

 Aster novae-angliae (Chamber- 

 lain 35 ) three to thirteen; and in 

 Antennaria duel 57 ) they con- 

 tinue to divide until quite a tis- 



Fio. 48. — A, Sherardia arvensie. Em- * 

 bryo-sac before fertilization : low- 

 er antipodal acting as an hausto- 

 rium. B, CaUipdtit cucullaria, 

 showing lower antipodal still act- 

 ive after embryo and endosperm 

 are considerably advanced. — After 

 Lloyd. 106 



