298 BOTANICAL GAZETTE » [NOVEMBER 
cellulose walls, and between the primary cortex and the primary 
polystelic region is the zone which contains the secondary vascular 
bundles and shows the growth rings. 
The primary polystelic region, in transverse section, looks 
somewhat like an immense cornstalk, with large bundles toward 
the center and smaller ones at the outside; but the structure of the 
individual bundles is very different from that in corn, for the 
bundles in Aloe have no sheath and most of them are completely 
amphivasal. There seem to be two types of vascular bundles in 
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Fic. 6.—Aloe ferox: showing both types of primary bundles; 100 
this primary region. In one type the bundles have normal xylem 
and phloem, except that the phloem has very few companion cells 
(fig. 3). The other type is peculiar. The phloem begins to dis- . 
organize and finally disappears, while the lumen in both tracheids 
and vessels becomes clogged with the same material found in the 
disorganizing phloem. Some of this material can also be seen 
surrounding the bundle itself. An early stage, shown in fig. 4, and 
a later stage, shown in fig. 5, are characteristic. In the latter 
figure the contents of the xylem cells are much denser and the 
phloem cells have become almost indistinguishable, while the 
adjacent thin-walled parenchyma is crowding into the space left 
vacant by the disorganizing phloem. 
