CYCADALES 



135 



closes the pit and that communication between the jacket cells and 

 the central cell is only through fine strands of protoplasm (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 





^c::^.. 



1 '.•: 



140 



Figs. 139-144. — Haustoria of cycads: fig. 139, Cycas revoluta; Xiso; fig. 140, 

 the same X37S; figs. 141-143, Dioon edule; X800; fig. 144, Encepkalartos Lehmanii, 

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

 sulphuric acid; Xi,ioo. — Figs. 139, 140, after IKENO (27); figs. 141-143, after 

 Chambeklain (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 earUer 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). 



