Mar., iy 1 1.] 
The Classification of Plants, VI. 
2 95 
greater numbers involved, and the complexity of structure. This 
is especially true of the choripetalous families, where it is almost 
impossible for the mind to grasp the enormous number of types 
to be considered. 
The Thalamiflorac are the lowest dicotvls. The first order, 
the Ranales, constitute a parallel group to the hvpogynous 
Helobiae. The Ranales are closely followed by the Sarraceniales, 
Brassicales, and the lower Gerianales and Malvales. 
The Centrospermae are a small branch having its origin 
in the Thalamiflorae. Its lowest family, the Caryophyllaceae, 
indicates the relationship while the higher forms are greatly 
specialized, passing over into reduced apetalous and naked flowers 
with high development of the inflorescence. 
The Calyciflorae represent another great, fundamental branch 
of choripetalous dicotyls arising from near the Ranales, but some- 
what more specialized. The lower genera of Rosaceae show 
marked resemblances to some Ranunculaceae. The other fam- 
ilies placed in this subclass are fairly certain and there may be 
families and genera at present associated with other subclasses 
that properly belong here. 
The Amentiferae are a small but important group whose real- 
tionship may be traced from the lower Calyciflorae through the 
Hamamelidaceae, Platanaceae, Ulmaceae, Moraceae, etc., up to 
the Salicaceae. A number of families now included are uncertain. 
One of the structures of the group is the highly specialized flower 
cluster, the catkin, and there are other significant features as 
chalazogamv besides various peculiarities of buds, twigs and leaves. 
The Myrtiflorae are an epigynous branch, mostly of chori- 
petalous dicotyls, probably derived from the Calyciflorae, from 
the vicinity of the Saxifragales. Some of the families may be 
excluded in the future but the main mass represents a distinct 
type of floral development and appears to be phylogcnetically 
related, excepting, perhaps the cactales which may even belong to 
the Centrospermae. 
The Heteromerae appear to have come from near the same 
region as the Centrospermae. The strong resemblance of certain 
Caryophyllaceae to Primulaceae is very suggestive and gives 
support to this view. The Heteromerae also show their primitive 
character by frequent choripetaly and other peculiarities. 
From the lower Heteromerae it is but a step to the Tubiflorae, 
the lowest forms of which are represented by the Convolvulaceae 
and Polemoniaceae. The families of the Tubiflorae are for the 
most part quite certain, except perhaps the Plantaginaceae. 
The last and highest subclass of Dicotylae, the Inferae, appears 
to be an offshoot from the lower Calyciflorae, the line leading 
almost directly from the Saxifragales to the Umbellales, Rubiales, 
Campanulales, and Compositales. 
