BENNETTITALES 



47 



numerous mucilage cavities in the pith, some of them several cells 

 wide. 



The histological details of xylem and phloem are beautifully pre- 

 served, but the delicate cells of the cambium are broken (fig. 40). 

 Transverse sections at about the middle of the xylem region and the 

 middle of the phloem region are shown in figs. 41 and 42. 



Fig. 40. — Cycadeoidea wielandii: c, cambium mostly broken down; above it the 

 phloem with many thick-walled tracheids, and below, the secondary wood. Xioo. — 

 After WiEL.vND.^'o 



Most of the tracheids are sclariform, but those of the protoxylem, 

 next to the pith, are spiral. No pitted tracheids were observed in 

 Cycadeoidea wielandi, although the preservation is so excellent that 

 they could hardly escape notice, if present. However, Lignier^^" 

 found bordered pits on the radial walls of tracheids of Cycadeoidea 

 micromela, and there are some bordered pits in Cycadeoidea painei 

 and dartoni. The markings on the tracheids should receive most criti- 



