2 I 8 
Hill and de Fraine. — On the 
13-15). At the same time the opposing bundles move towards the cotyle- 
donary plane until their metaxylems are contiguous (Diagram 11, Fig. 16 ) ; 
at a lower level the corresponding groups of phloem elements join together ; 
thus a diarch root-structure obtains. A comparison of the critical stages 
shows that the transition phenomena of A. brasiliensis are essentially like 
those of A. Cunninghamii , although, in the former plant, they appear more 
complicated owing to the greater number of cotyledonary vascular bundles, 
and the large amount of plumular vascular tissue. This similarity may be 
seen by a comparison of figures 5, 6, 13-16 in Diagram 11 with Figs. 2-5 of 
Diagram 10. 
The resemblance is the more marked when reference is made to Stras- 
burger’s 1 brief description of the transition-phenomena in this same species 
(A. brasiliensis ), which account describes what we have found to obtain in 
A. Cunninghamii , with the exception that in the latter plant there are four 
bundles for each cotyledon, and in A. brasiliensis there are eight. We our- 
selves found fewer vascular strands, but it is likely that eight is the typical 
number for each seed-leaf of the hypogeal forms, for Seward and Ford 2 give 
this number for the cotyledons of A. imbricata ; on the other hand 
Dangeard 3 states that seven strands occur in the seed-leaves of this species 
(A. imbricata). 
To return to the minor features in the transition-region of A. brasili - 
ensis (Series A) ; there is a tendency for some of the vascular strands to 
detach portions which gradually become smaller and die away at lower 
levels ; in other words, the large bundles give off smaller branches which 
end blindly (Diagram 11, Figs. 10 and 14). At a much lower level a branch, 
consisting only of xylem, and very much smaller than those mentioned 
above, was given off and appeared in transverse section as a finger-like 
process. This strand underwent an exarch displacement, and followed 
a sinuous course downwards, being, at different levels, alternately attached 
to and detached from the main bundle from which it took its origin. 
Ultimately, it died away (Diagram 11, Figs. 11 and 12, in which the portions 
illustrated are of the strand marked with an * in Fig. 10). 
Series B. This seedling was in the stage represented in Figure 5, 
Plate XV. Secondary thickening was well advanced, and each cotyledon, 
had five vascular bundles at its base. Some of these strands, in the cortical 
region of the uppermost part of the hypocotyl, fused together so that two 
groups of four bundles resulted. The transition took place in the manner 
described above for Series A. 
The seedling anatomy of A. imbricatah&s been described by Dangeard 4 
and Seward and Ford. 5 Dangeard states that at the base of the cotyledons 
the bundles unite tangentially to form two large elongated strands, which 
in the hypocotyl divide into two. Thus there are four large bundles which 
1 loc. cit. 2 loc. cit. 3 loc. cit. 4 loc. cit. 5 loc. cit. 
