CYCADALES 



135 



closes the pit and that communication between the jacket cells and 

 the central cell is only through fmc strands of j)rotoplasm {Plasmodes- 

 men) traversing the pit-closing membrane, and claim that it would 

 be absurd to suggest that protein granules travel from the jacket cells 

 to the central cell. In Dioon edule, according to Chamberlain (46), 



139 



.40 •: :. 



Figs. 139-14;. — -Haustoria of cycads: fig. 139, Cycas revoluta; X150; fig. 140, 

 the same X375; figs. 141-143, Dioon edule; X800; fig. 144, Encephalartos Lehmanii, 

 showing the Plasmodesmen; from a free-hand section which had been treated with 

 sulphuric acid; X 1,100. —Figs. 139, 140, after Ikeno (27); figs. 141-143, after 

 Ch.\mberl.-\in (46); fig. 144, after Stopes and Fujii (50). 



substances pass from the jacket cells into the haustoria as readily 

 as from one part of the cell into another. Doubtless a pit-closing 

 membrane exists here, as elsewhere, during the earlier development 

 of the central cell, but as the haustoria grow larger and project into 

 the cells of the jacket, the closing membrane is ruptured. The 

 situation may be better understood from a series of figures by the 

 various investigators (figs. 139-144). 



