166 de Fraine.— The Seedling Structure of certain Cactaceae. 
Anemarrhena asphodetoides . So far as has been ascertained this formation 
of a tetrarch root-stele from two cotyledonary traces has been previously 
described in only two other dicotyledonous seedlings, Eranthis hiemalis 1 
and Podophyllum peltatum , 2 in both of which the tetrarch arrangement 
is fugitive and the root is really a diarch structure. In the Cactaceae, on 
the other hand, the resemblance to Anemarrhena is more complete, for the 
tetrarch structure persists to the root-tip ; indeed, the only important 
difference between the two seems to lie in the fact that the two cotyledonary 
bundles are derived in the Cactaceae from two seed-leaves and in Anemar¬ 
rhena from one. 
The occurrence of the Anemarrhena type in a modified form in a 
member of the natural order Ranunculaceae which, on other grounds, has 
been considered to bear a somewhat close relation to the Monocotyledons, 
has been used as a reason for formulating an hypothesis as to the origin of 
the monocotyledonous condition, namely, a theory that ‘ the two cotyledons 
of Primitive Angiosperms have united to form the single member in 
Monocotyledons \ 3 The close resemblance between Eranthis and Anemar¬ 
rhena led to the conclusion that there is probably ‘ a real genetic connection 
between Eranthis and Anemarrhena\ that they are descended from a 
common ancestor with two distinct seed-leaves, each represented by a single 
trace in the hypocotyl \ 4 Now the cotyledons of Eranthis are united 
as regards their petioles, and this led to the statement that even if there 
were no historical connexion between them, ‘ the structure of Eranthis may 
nevertheless illustrate the double origin of the Anemarrhena cotyledon. 
For without the analogy of Eranthis , the assumption that each trace in the 
cotyledon of Anemarrhena represented a distinct seed-leaf was groundless. 
Not only was direct evidence of such a double origin absent, but there was 
nothing to show that the union of two cotyledons, if it did take place, would 
actually give rise to such a type of vascular symmetry.’ The second 
Dicotyledon in which the Anemarrhena type was found was also a 
geophilous seedling in which the petiolar tube was well developed ; hence 
the ‘ fusion ’ hypothesis appeared to receive additional support, for the 
known facts seemed to show that union of cotyledons might bring about 
such a vascular arrangement as was found in Anemarrhena. But at the 
same time it must be observed that the formation of a cotyledonary tube 
does not necessarily produce this Anemarrhena type of structure, for in two 
other Ranunculaceous seedlings, Delphinium sp. (probably nudicaule) and 
1 Sargant, E. : The Origin of the Seed-Leaf in Monocotyledons. New Phyt., i, 1902, p. 112. 
2 Sargant, E. : Reconstruction of a Race of Primitive Angiosperms. Ann. Bot., xxii, 1908, 
p. 170. 
3 Loc. cit., p. 183. 
4 Sargant, E. : A Theory of the Origin of Monocotyledons, founded on the Structure of their 
Seedlings. Ann. Bot., xvii, 1903. 
