8c>4 Compton. — 'An Anatomical Study of 
primitive Dicotyledonous families as the Ranales, and are most probably, 
therefore, themselves primitive as compared with other Monocotyledonous 
families. The Helobieae are, however, remarkable among Monocotyledons 
in possessing exalbuminous seeds. The Ranales, on the other hand, are 
typically albuminous. No order of Dicotyledons yields so many tube- 
forming syncotyls as the Ranales, and we may perhaps expect a similar 
tendency to apply all through the Ranales-Helobieae alliance. Now we 
have seen that syncotyly in albuminous species usually produces a cotyle- 
donary tube, but that in exalbuminous species the cotyledons tend to fuse 
on one side only. It is therefore probable that if the Helobieae are 
descended by syncot}dy from exalbuminous dicotyls, the fusion of cotyledons 
would take place along one edge, and we should obtain an embryo sym- 
metrical about one plane only, and not about two, as in the tube-forming 
Ranales. This form of embryo is what we actually find in the Helobieae 
— and, indeed, in the more advanced Monocotyledons generally, where 
the asymmetric condition may well persist in spite of endosperm in the 
seeds. 
We may conclude that (i) syncotyly is a single phenomenon wherever 
it occurs, whether affecting one or both edges of the cotyledons ; the 
differences being due to space and symmetry relationships within the 
developing seed, (ii) Since one-sided syncotyly is the form produced in 
exalbuminous seeds, this is what would be expected to occur in the primitive 
and exalbuminous Helobieae if that family had adopted syncotyly. (iii) The 
Liliifloreae, which according to modern views are very possibly derived from 
plants sharing many characters of the Helobieae, have retained certain 
primitive features, and among them tetrarchy and a seed-leaf with two 
equal vascular bundles as in Anemarrhena , though not in the majority 
of species. 
'■ / • ■ ’ . A ' f:"' ■" / 
Syncotyly has a more or less pronounced influence upon the vascular 
structure according as the typical anatomy is complex or simple. In the 
Ranunculaceae the structure of apocotylous and syncotylous species is 
closely similar, the diarch root and two double-bundles in the cotyledon 
occurring throughout ; this is so whether a tube be present, as in most 
syncotylous species , 1 or whether syncotyly be one-sided, as in Ranunculus j 
chins . 2 The same is true of the relatively simple Swainsona Cadelli , 
where, be it noticed, the base of the seed-leaf only contains two vascular 
strands, though the root is triarch. In the larger species, such as Helianthns 
annuus and Primus domestica , where lateral cotyledon traces are present, 
syncotyly leads to elimination and compression of vascular bundles, together 
with reduction in the type of symmetry in the root. 
The ‘ Anemarrhena type’ of vascular structure is characterized by the 
1 Sterckx (’99). 2 Sargant (’03), p. 65 . 
