294 
H. F. Wernham. 
Two fundamental characters stand out as almost unexceptionally 
constant throughout the Tubiflorse ; first, the ovary is superior, and 
second, the carpels are two in number. It need scarcely be stated 
that the corolla is invariably sympetalous ; and the stamens are 
epipetalous, sometimes at the base, but usually in the tube, throat, 
or mouth of the corolla. 
The cohort Tubiflorae of Engler falls naturally into three main 
divisions. In the first, the connection between this cohort and the 
Contortse is observable, the flowers being prevailingly regular or 
sub-regular, and the androecium isomerous with the corolla; this 
may be regarded as a transitional group. In the second and third 
divisions the flower is almost invariably zygomorphic; in one of 
these two the ovules regularly number two, rarely one, per carpel; 
in the other the number of ovules is prevailingly indefinite. 
Bentham and Hooker ascribe cohortal rank to each of these 
three divisions, naming them respectively Polemoniales, Lamiales, 
and Personales. In Engler’s system they are treated as sub-cohorts, 
or divisions of a single cohort, the Tubifloras; further, the Acanthaceae 
and Myoporaceae are each assigned therank of separate divisions, 
making five in all. 
It will be well to consider these three groups in order separately. 
The Transitional Group. 
This group, characterized by regularity of the flower and 
isomery of the androecium with the corolla, is represented by group 
A of Engler’s system and the cohort Polemoniales of Bentham and 
Hooker; the typical characters of the natural orders comprising 
this cohort, together with the relations between the two systems, 
are displayed in the accompanying table. The essential difference 
between them is the inclusion by the older authors of the Solanaceae 
in their transitional group; we shall have need to return to this 
important point later. For our immediate purpose we shall follow 
the older system in this regard. 
The largest natural orders concerned, then, are Solanacese 
with 1,500 species; Boraginaceae, with 1,200 species; and Convol- 
vulaceae, with 1,000 species. A brief consideration of the latter 
two leads to the conclusion that they both reflect high evolutionary 
advance, each upon a special line. The characters of the constituent 
species of both are remarkably constant throughout. The habit, 
in the first place, is characteristic in each case—the climbing, 
herbaceous or sub-herbaceous habit of the Convolvulaceae, with 
their generally large, funnel-shaped flowers and alternate leaves, 
