de Fraine .— The Seedling Structure of certain Cactaceae. 141 
tion of the intercotyledonary arms, would result in the curious structure 
seen in most of the roots of the seedling Cerei. 
Cereus Jamacaru , D.C. The transition-phenomena of these seedlings 
were practically identical with those of C. tortuosus ; there were, however, 
one or two differences of minor importance. For instance, the seedling 
had no lateral bundles in the cotyledons, and the strand which supplied the 
cotyledonary bud was very small, dying out before reaching the seed-leaf- 
trace. In another seedling four lateral roots arose almost simultaneously, 
alternating with the phloem groups ; in general only two appear, and these 
opposite the protoxylem. 
Cereus Spachianus , Lem. Both in the transition-phenomena, and 
in other respects, the seedlings of this plant closely resemble those of 
C. Jamacaru. 
Cereus triangularis , Mill. With the exception that the cotyledonary 
bud is but slightly developed, and has no vascular supply, the structure and 
transition-phenomena in these seedlings are similar to those of C. tortuosus. 
PlLOCEREUS. 
The two species of Pilocereus which were examined showed a great 
similarity to Cereus in their external appearance; and, as in some species 
of that genus, small cotyledonary buds were present in the axils of the 
seed-leaves. 
Pilocereus exerens , K. Schum. Each of the two cotyledons has a small 
endarch bundle throughout its length, and at its base the slightly differentiated 
tubercle-bundle appears. The seed-leaf-traces and the tubercle-bundles 
in Series 1 perform differently: in one cotyledon they form the ‘double’ 
bundle in exactly the same way as is illustrated for Cereus peruvianus 
(Diagram 6, Figs. 2, 3), in the other cotyledon the seed-leaf-trace shows no 
bifurcation of its phloem, but rotating slightly, forms one half of the ‘ double ’ 
bundle, the second half being produced by the tubercle-bundle. The two 
‘double’ bundles once formed, the transition is practically completed, since, 
except for a slight centripetal displacement of the vascular elements, no 
further changes take place, and the root is of the Cereus type. In Series 2 
both cotyledon-bundles bifurcate, and the tubercle-strands, in which no 
xylem is present, fuse laterally with one half of the seed-leaf-phloem ; in 
other respects the transition takes place as in Series 1. 
Pilocereus albispinus , Salm-Dyck. 
Series 1. Each cotyledon contributes one endarch bundle to the 
hypocotyl, and also one tubercle-bundle which is composed of phloem 
only. The tubercle-phloem-strand bifurcates, and the two halves pass 
outwards until they lie one on either side of the cotyledonary bundle ; the 
phloem of the latter then bifurcates, and the two halves separate slightly 
and fuse with the adjacent tubercle-phloem groups. Further rotation of 
