136 de Frciine .— The Seedling Structure of certain Cactaceae. 
The seedlings of this species thus show a method of transition from 
stem to root structure which is essentially of the Anemarrhena type, but 
in the one case the c double ’ bundles are derived from two cotyledons, 
while in the latter they are furnished by a single one. 
PHYLLOCACTUS. 
Seeds of various species of Phyllocactns were planted, but only one set 
germinated. 
Phyllocactns Hookeri , Walp. These seedlings showed 
a somewhat succulent hypocotyl, with two short cotyledons, 
which in form and in their degree of fleshiness resembled 
those of Cereus tortuosus (Fig. 7). In general characters 
the structure of the cotyledon and hypocotyl is very 
similar to that of species of Cereus ; and in three of the 
four seedlings examined, a small cotyledonary bud occupied 
the base of the cotyledon, although in one case only did 
this bud possess a vascular supply. 
Fig. 7. 
Phyllocadus 
Hookeri. x 2. 
Transition. 
1. Series A, B, and C, in which the bundle of the cotyledonary bud 
was absent. 
Each of the cotyledons possessed one small endarch bundle ; in one 
seedling the bifurcation of the phloem took place before the entrance into 
the hypocotyl, in the others it was delayed for some time, and in no case 
did any division of the xylem occur. Four very small and ill-differentiated 
epicotylar strands were present in the upper part of the hypocotyl, but 
these played no part in the formation of the root, and their differentiation 
soon ceased. The half-phloems of the cotyledonary bundles separated and 
left the xylems isolated, the wood consisted of a few somewhat scattered 
elements, and the protoxylems attained the exarch position rather by 
a rearrangement of the elements than by a definite rotation. Towards the 
base of the hypocotyl a loose central strand of wood is produced by the 
centripetal development of tracheides; at the same time the opposite 
phloem groups gradually approach as though fusion were about to take 
place; a junction however is not effected, and the phloems separate again, 
so that the root-structure is of the type found in Cereus , in which there are 
four phloem- and two xylem-bundles. 
2. Series D, in which the bundle of the cotyledonary bud was present. 
The cotyledonary bud in this seedling was poorly developed and 
consisted of a tiny mass of parenchymatous tissue with a few multicellular 
hairs, but it was provided with a vascular supply. Besides the two 
cotyledonary bud-bundles and the two endarch cotyledon-strands, there 
were in the upper part of the hypocotyl four epicotylar traces. The 
