1906] CHAMBERLAIN—OVULE OF DIOON 337 
passing through them, and in passing undergoing some change before 
reaching the endosperm. It may be that the peculiar nuclear condition 
is brought about by the extreme activity of the jacket cells. 
The walls of the jacket cells are suberized and stain deeply with 
safranin, thus contrasting sharply with the cellulose walls on both 
sides of them. The most conspicuous cell contents are irregular 
granules and coarse strands, which stain so deeply with safranin that 
in a section of a November ovule the jacket appears as a bright red 
circle easily visible to the naked eye. The material of the granules 
appears very much like that of the outer part of the megaspore mem- 
brane, which Tomson (21) found to be a suberized structure. He 
described similar granules in other cycads and found them to consist 
of amylodextrin, but in his form the amylodextrin disappeared before 
the stage represented in jig. 13 was reached. (There are no pits in 
any of the cells of the jacket.) The irregular granules and strands 
adhere closely to the cell wall even after the cytoplasm has been drawn 
away by reagents, as shown in figs. 12 and 13. No granules or 
strands are found on the outer walls of the jacket cells or in the cells 
on either side of the jacket layer. The endosperm jacket differs 
decidedly from the archegonial jacket in having no pits in the walls; _ 
Consequently, all substances must pass through the jacket by the 
usual method of transferring material from one cell to another. _ 
The jacket is doubtless concerned with the nutrition of the struc- 
tures within, like the jacket about the embryo sac of an angiosperm, 
the jacket about the seeds of gymnosperms, or the tapetum about the 
Spotogenous cells of microsporangia. While the jacket in all these 
cases is concerned in nutrition, the mode of nutrition and the nature 
of it are different. It is most active while the endosperm is still 
Spherical. As the endosperm elongates and approaches its full size, 
the jacket disintegrates, and at the stage shown in fig. ro it has broken 
up and only suberized fragments remain. As to its morphological 
nature, the jacket corresponds to the jacket or tapetum which sur- 
tounds the sporogenous tissue of microsporangia. In a microspor- 
angium the jacket surrounds a large number of spores, while in the 
“ase under discussion it surrounds only one spore, which, at the stage 
shown in jig. 10, has developed an extensive prothallium. Lane (12), 
who secured early stages of this structure in Stangeria, describes an 
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