de Frame .— The Seedling Structure of certain Cactaceae, 143 
Transition. 
Echinocerens Ehrenbergii , Engelm. The cotyledons have at their 
broadest part five small vascular bundles, which by anastomosing have 
been reduced, by the time the base of the cotyledon is reached, to two in 
one cotyledon (c x ) and one in the other (c 2 , Diagram 7, Fig. 1). 
During the passage into the hypocotyl the phloem of the bundle c 
bifurcates and the two halves rotate round the protoxylem ; no metaxylem 
is present. The two bundles in c 1 rotate slightly until their protoxylems 
are directed towards one another. Six epicotylar phloem groups (e) are 
also shown in the hypocotyl at this level (Diagram 7, Fig. 2), but fusion 
of two of the adjacent bundles soon reduces their number to four. 
These four groups ultimately join with the cotyledonary phloem next to 
Diagram 7. Echinocerens Ehrenbergii. 
them, but before this is accomplished the two protoxylems of c x have 
fused. A diarch root finally results by the union of the two adjacent groups 
of bast (Diagram 7, Figs. 3 and 4). 
Series 2 showed two differences from the transition just described : 
there were fewer bundles in the cotyledons, and the two ‘ double ’ bundles 
of the hypocotyl were both produced as in c x (Diagram 7) by the union of 
two strands, not by the bifurcation of one. 
Echinocerens cinerascens , Lem. These seedlings had only three bundles 
in the cotyledons, which fused towards the base into a single strand, 
bifurcation of which took place during the passage into the hypocotyl. 
With the exception that no epicotylar phloem was developed, the transition 
was essentially like that in E. Ehreyibergii. 
Echinopsis. 
The seedlings belonging to the Echinopsis group are distinctly smaller 
than those of the genus Cerens. They are characterized by an almost 
