THE FEMALE GAMETOPHYTE 113 



antipodal portion of the sac. This type is characteristic of 

 Sympetalae, perhaps being especially prominent among the 

 Kubiaceae and Compositae; but it is also conspicuous among 

 the Gramineae and Amentiferae. Among the Amentiferae it 

 is noteworthy that an antipodal haustorium occupied by active 

 antipodal cells and a special vermiform haustorium occupied 

 by endosperm cells are often both present. 



That every suspensor is an haustorium for the embryo 

 seems evident, but aside from this general fact special out- 

 growths from the suspensor are developed to reach a wider 

 range of nutritive supplies. The case of certain orchids whose 

 suspensors develop vermiform haustoria that envelop the em- 

 bryo, or grow through the micropyle and embed themselves in 

 the wall of the ovary, has long been known; and it has been 

 recently found that among certain Rubiaceae (Galieae) the 

 filamentous suspensor sends out conspicuous lateral processes 

 or branches that penetrate the endosperm (Lloyd 105 ). 



In some cases a complex mechanism for nutrition has been 

 described, and numerous others will be discovered when atten- 

 tion is given to the subject. The case of Phlox Drummondiij 

 as described by Billings, 100 may be used as an illustration. The 

 wall of the ovary adjacent to the micropyle develops a papilla 

 of special structure consisting of elongated cells. This presses 

 against the micropyle, which becomes closed and resembles con- 

 ducting tissue. A papilla of small cells develops from the adja- 

 cent integument in contact with the sac, and pressing into it is 

 put in connection with the suspensor. In testing this mecha- 

 nism for starch, Billings found starch in the ordinary tissue of 

 the ovary wall, no starch in the wall-papilla, and abundant 

 starch again in the integument bordering the old micropyle. 

 This seems to establish a definite passage of nutritive supplies 

 from the ovary wall, through a series of specially developed 

 tissues, to the suspensor. 



In Stylidium squamellosum (Burns 85 ) there is a remarkable 

 combination of nutritive structures (Fig. 50). The micropylar 

 end of the sac enlarges enormously and spreads out through the 

 thick integument, a remarkable nutritive jacket of radially 

 elongated cells invests the lower part of the sac, and a distinct 

 gland-like nutritive tissue is developed in the chalaza adjacent 

 to the antipodal end of the sac. 



