556 Thiselton-Dyer . — Morphological Notes. 
Decaisne, and he remarked that he thought there was a ten- 
dency in Acer to a ternary distribution of parts, reminding 
me that the sycomore occasionally develops a third samara 
in its fruit. This is true, but in the Kew Museum there is 
a series of fruits of the common maple {Acer campestre ) in 
which the number of samaras varies from two to eight : it is 
therefore apparently fluctuating. 
In PI. XXIV, Fig. i, I have illustrated a case similar to 
those which Duchartre studied. In Fig. 3 I have shown one, 
which he apparently did not meet with, in which three coty- 
ledons are followed by a pair of opposite leaves, one of which 
is bipartite. In the former, according to Duchartre’s view, the 
embryo started with a pair of cotyledons, one of which sub- 
sequently branched. This, however, is a priori an improbable 
supposition, as cotyledons, unlike leaves, are generally simple 
and, except in the somewhat rare cases now under discussion, 
rarely show any disposition to be otherwise. 
Masters (Vegetable Teratology, p. 37 o) gives several in- 
stances of tricotyledonous embryos, to which I may add one 
in the oak for which I am indebted to a former pupil, 
Mr. G. Cross. Masters quotes Reinsch for a seedling beech 
‘ associated with a union of the margins of two out of the 
three cotyledons, and of those of two out of the three leaves 
next adjacent.’ Masters thinks with Duchartre that c some of 
these cases may be accounted for by chorisis or by a cleavage 
of the original cotyledons.’ 
I arrive, however, at the conclusion that the simplest expla- 
nation is, that in all the cases now described, the embryo is 
provided with three instead of two primordial lateral out- 
growths, and that these either develop completely into three 
normal cotyledons or that two of them sooner or later coalesce 
into one which is more or less deeply bifid. If this explana- 
tion is true of cotyledons it must equally apply to the similar 
phenomena exhibited by the epicotylar leaves. 
Professor Bayley Balfour looks upon the cotyledons as 
‘ suctorial organs,’ and in cases where an endosperm is present 
this is no doubt true. But an inspection of the large series 
