H. F. Wernham. 
160 
The Diovulatae. 
The essential characters of this group are included in the table 
on p. 152, and their affinities indicated in the diagram on p. 152. 
A striking feature in regard to this branch as compared with the 
Multiovulatse is the small number of families—practically three 
only—into which it may be naturally divided; and of these over 
75% fall into one very natural family, Labiatse. 
The key-note of the Diovulatse, we have seen already, is schizo- 
carpy, the tendency to associate each seed with a separate fruit¬ 
covering, This tendency we have discovered in the Transitional 
Group, and we have observed it in a high degree of realization in 
Boraginaceae. 
Schizocarpy clearly involves reduction in the number of ovules; 
this is reflected in a leading character of Diovulatae, namely, the 
presence of two ovules only to each carpel. This character is 
remarkably constant throughout the group, as is also the bicarpellary 
condition of the ovary, although in some cases the true primary 
structure is masked by the early initiation of secondary septation. 
The largest group, Labiatae, is so well-defined for the most part, so 
constant in essential characters, and possessed of so characteristic 
a “facies,” that we are led to a prima facie presumption that it is 
relatively advanced ; this, we shall find, is probably the case. 
The remaining members of the Diovulatae are comprised in the 
families Verbenacese (with Phrymaceae) and Myoporaceae. 
We may premise that Verbenaceae display many evidences of 
relative primitiveness. In the first place, many trees and shrubs 
are included in the family, and a good number with compound 
leaves ( Vitex ). In no small proportion (about 14%), again the corolla 
is nearly or quite regular with isomerous andrcecium (some 
Chloantheae and Viticeae). In nearly 80% of the family oligomery 
of the andrcecium has proceeded only so far as the abortion of one 
stamen of the ancestral pentamerous whorl, 1 leaving barely 8% with 
diandrous flowers—a somewhat striking contrast with the corres¬ 
ponding figures for Scrophulariaceae, 30%, and Acanthaceae, 50%. 
Even in Labiatae, we shall find, diandrous flowers occur in less than 
25% of the species, so that in this regard the Diovulatae as a whole 
are not nearly so far advanced as the Multiovulatae. 
1 Curiously enough, however, all trace of the ancestral posterior 
stamen has been lost in the ontogeny of those forms examined 
by Payer (loc. cit. p. 559). He finds that only four staminal 
primordia are laid down in the case of Lippia citriodora, L. 
repens, L. chamcedrifolia, Verbenapulchella, and Spielmannia africana ; 
a pair of anterior stamens appear first, then two lateral 
members. 
