5° BOTANICAL GAZETTE [JULY 
later becoming fused into a reticulated skeleton, the separate 
bundles of a single strand also anastomosing. The wavy line 
formation is seen to a slight extent in these Cylindropuntias 
also; there is apparently no branching, and little increase in 
width of bundle. The phloem presents no unusual characters ; 
the xylem is composed of annular ducts, with 
flat rings at regular intervals; later on there 
occur also spiral tracheids, with steps grading 
to the true trachea. 
In an earlier article the roots of this species 
have been referred to as anchoring and absorp- 
tive. Portions of the xylem of each are 
figured here to show the difference in texture 
(figs. 7,8). In the absorptive roots the elements 
are wider, more regular, and less thickened. 
The phloem differs but slightly in the extent 
of development of sieve tubes; the xylem dif- 
ers as usual in proportions of elements, con- 
sisting in both of scalariform tracheids and 
fiber tracheids. From the prominence of the 
latter, both here and elsewhere, it would appear 
that the main function, if not the only one, 
which this element performs in the Cactaceae 
tionof portionof is one of support. 
xylem from absorp- OPUNTIA ARBUSCULA Engelm.—The hypo- 
— of Opuntia derma is fairly thick, with a compact deposit 
OnE atte ier of crystals in the outermost layer. The assimi- 
tionof portion of lative tissue is compact, the cells being small 
xylem from anchoring and greatly elongated inregions near the sur- 
pa of Opuntia ful- face. The chloréphyll/extends through the 
: thin-walled parenchyma as well. Crystals are 
very abundant throughout, varying considerably in size and com- 
pactness of aggregation. The stem is very turgid and mucilagi- 
nous, kept rigid by turgor for some time, with late bundle 
development. The-bundles finally form the same kind of reticu- 
lated skeleton seen in O. fulgida. The phloem is as usual; the 
