Seedling Structure of Gymnosperms . II. 193 
with half the phloem of c ; again the protoxylems of a and d retain their 
identity longer than would be expected if these two strands represented the 
bundles of half-cotyledons ; further, from what obtains in the similar seed- 
ling of Cupressus tondosa , and in other plants to be described hereafter, the 
bundles a and b would be expected to form one pole of the root, since these 
are the traces of the two cotyledons which fuse together ; finally, the proto- 
xylem of d becomes exarch, and, at a lower level, makes its way through 
the metaxylem to join with the protoxylem of a. These characteristics 
are not those associated with the strands of either half-cotyledons or subsi- 
diary cotyledons ; for these reasons this particular seedling may be looked 
upon as an example showing a tetrarch root-structure becoming triarch in 
a very short space. The fusion of the seed-leaves a and b is the beginning 
of the formation of a cotyledonary tube which is not at all uncommon in 
these polycotyledonous forms. 
Abies Veitchii. Of this species, only one seedling, having three cotyle- 
dons, was available. The transition-phenomena leading to the formation of 
the root-structure, although similar to what occurs in A. sibirica (Series A), 
is not nearly so well marked as in the last-named plant. The redistribution 
of the xylem elements in order to bring the protoxylem into the exarch 
position is of a very indefinite nature, there being in two bundles no separa- 
tion of the xylem masses into two halves followed by a rotation (cf. 
Juniperus *) ; the xylem of one bundle did, however, partly split in the 
manner described for Actinostrobusp but the V very soon closed up again. 
Abies balsamea , Mill. All the plants of this species had four cotyledons, 
each with one vascular bundle. 
The transition resembles A. sibirica in all essentials, but the rotation 
of the protoxylem is not so well marked in all cases, a character which 
recalls that obtaining in Callitris rhomboidea . 3 
Series A. Two of the cotyledonary bundles underwent bifurcation 
and rotation to form two poles of the triarch root ; the two remaining seed- 
leaf-traces together formed the third pole. 
Series B. All the four vascular bundles derived from the seed-leaves 
showed bifurcation and rotation of their vascular elements, a tetrarch root- 
structure resulting. The exarch position of the protoxylem, however, was 
brought about partly by the rotatory movement and partly by an indefinite 
rearrangement of the xylem-elements. 
Series C proved more interesting. Of the four cotyledonary bundles, 
three exhibited bifurcation and rotation of the xylem as in the other plants 
of this species ; in a very short space, however, half the xylem of one of 
these strands, which, for convenience may be termed c } fused with the xylem 
of the adjoining fourth seed-leaf-trace (d), and the combination of the two 
gave rise to one pole of the triarch root-structure. The fourth bundle was 
1 Part I, Annals, 1908, p. 696. 2 Part I, Id. p. 703. 3 Part I, Id. p. 706. 
