The Cactacece and the Study of Seedlings. 335 
that “ the evidence on which the ‘ fusion ’ hypothesis was based has 
been considerably weakened by the discovery of the Anemarrhena 
type in seedlings of such a specialized order as the Cactaceae.” 
It will be admitted that the force of Miss de Frame's argument 
depends very largely upon the systematic position to he assigned to 
the Cactaceae—a subject which she does not discuss. There can, 
of course, be no question but that this order is “ specialized ” as 
regards its vegetative characters, but it is the reproductive organs, 
and not the vegetative features of the mature plant, which are of 
prime importance as regards affinities. As Darwin wrote in the 
chapter on “ Classification ” in the Origin of Species,—“ With 
plants how remarkable it is that the organs of vegetation, on which 
their nutrition and life depend, are of little signification; whereas 
the organs of reproduction, with their product the seed and embryo, 
are of paramount importance ! ” 1 
The Cactaceae are usually regarded as an isolated group of 
obscure affinities, and in different systems of classification they occupy 
very various positions. For instance Engler and Prantl 3 place the 
Cohort Opuntiales, containing the single order Cactaceae, between 
the Parietales and the Myrtiflorae. In Potter’s translation of 
Warming’s Systematic Botany, 3 on the other hand, the Cactiflorae 
(corresponding to Engler’s Opuntiales) are placed immediately before 
the Polycarpicae (otherwise called Ranales). An examination of 
the floral characters leads one to suppose that the latter position 
gives perhaps the best indication of the true affinities of the 
Cactaceae. They have a remarkable number of features in common 
with various members of the Ranalian plexus, especially those 
which are regarded by some authors as retaining many primitive 
characters, such as the Nymphaeaceae and Magnohaceae. The most 
striking of these “Ranalian” characters are the following:—The 
flowers are noticeable for their acyclic structure,—there are 
numerous spirally arranged sepals, petals and stamens. In certain 
cases the floral leaves clothe the external surface of the receptacle, 
and there is a gradual transition between the small sepaloid, and 
the large brightly coloured petaloid members of the perianth. The 
carpels may be numerous. As regards the general structure of the 
flower, a marked similarity may be recognised by comparing the 
longitudinal sections of such flowers as Pilocereus (Cactaceae) 4 and 
Euryale ferox . 5 (Nymphaeaceae) in both of which the perianth tube 
is prolonged above the inferior ovary into a tubular structure on 
the inner side of which the stamens are inserted. 
If it is, as the present writer is inclined to think, a justifiable 
hypothesis that the Cactaceae are derived from the same ancestral 
stock as the Nymphaeaceae, and other orders belonging to the 
Ranalian plexus,—the occurrence of the “ Anemarrhena-Eranthis”- 
1 C. Darwin. “ Origin of Species,” Sixth Edition, p. 343, 1894. 
2 Engler & Prantl. “ Pflanzenfamilien.” Nachtrag zu Teil 
II—IV, 1897, p. 352. 
3 “A Handbook of Systematic Botany. E. Warming & M. C. 
Potter, 1904, p. 375. 
* Engler & Prantl. “Pflanzenfamilien.” III. 6a, p. 180, Fig. 
59, 1894. 
6 Engler & Prantl. “Pflanzenfamilien.” III. 2, p. 6, Fig. 7f, 
1891. 
